Source -> http://stackoverflow.com/questions/10322341/simple-algorithm-for-drawing-filled-ellipse-in-c-c

/// <summary>
        /// Draws a filled Ellipse.
        /// </summary>
        /// <param name="image">
        /// The destination image.
        /// </param>
        /// <param name="x">
        /// The x left most position of the ellipse.
        /// </param>
        /// <param name="y">
        /// The y top most position of the ellipse.
        /// </param>
        /// <param name="width">
        /// The width of the ellipse.
        /// </param>
        /// <param name="height">
        /// The height of the ellipse.
        /// </param>
        /// <param name="color">
        /// The color to use.
        /// </param>
        public static void FillEllipse<T>(this GenericImage<T> image, int x, int y, int width, int height, T color)
        {
            width = width / 2;
            height = height / 2;
            var centerX = x + width;
            var centerY = y + height;

            // source -> http://stackoverflow.com/questions/10322341/simple-algorithm-for-drawing-filled-ellipse-in-c-c
            for (var indexY = -height; indexY <= height; indexY++)
            {
                for (var indexX = -width; indexX <= width; indexX++)
                {
                    var dx = indexX / (double)width;
                    var dy = indexY / (double)height;
                    if (dx * dx + dy * dy <= 1)
                    {
                        image[centerX + indexX, centerY + indexY] = color;
                    }
                }
            }
        }

Source (converted from C++) -> http://www.dailyfreecode.com/Code/draw-ellipse-midpoint-ellipse-algorithm-714.aspx

/// <summary>
        /// Draws a Ellipse.
        /// </summary>
        /// <param name="image">
        /// The destination image.
        /// </param>
        /// <param name="centerX">
        /// The x center position of the circle.
        /// </param>
        /// <param name="centerY">
        /// The y center position of the circle.
        /// </param>
        /// <param name="width">
        /// The width of the Ellipse.
        /// </param>
        /// <param name="height">
        /// The height of the Ellipse.
        /// </param>
        /// <param name="color">
        /// The color to use.
        /// </param>
        public static void DrawEllipse<T>(this GenericImage<T> image, int centerX, int centerY, int width, int height, T color)
        {
            // source (converted from C++) -> http://www.dailyfreecode.com/Code/draw-ellipse-midpoint-ellipse-algorithm-714.aspx
            float aa = (width * width);
            float bb = (height * height);
            float aa2 = (aa * 2);
            float bb2 = (bb * 2);

            float x = 0;
            float y = height;

            float fx = 0;
            float fy = (aa2 * height);

            float p = (int)(bb - (aa * height) + (0.25 * aa) + 0.5);

            image[(int)(centerX + x), (int)(centerY + y)] = color;
            image[(int)(centerX + x), (int)(centerY - y)] = color;
            image[(int)(centerX - x), (int)(centerY - y)] = color;
            image[(int)(centerX - x), (int)(centerY + y)] = color;

            while (fx < fy)
            {
                x++;
                fx += bb2;

                if (p < 0) p += (fx + bb);

                else
                {
                    y--;
                    fy -= aa2;
                    p += (fx + bb - fy);
                }

                image[(int)(centerX + x), (int)(centerY + y)] = color;
                image[(int)(centerX + x), (int)(centerY - y)] = color;
                image[(int)(centerX - x), (int)(centerY - y)] = color;
                image[(int)(centerX - x), (int)(centerY + y)] = color;
            }

            p = (int)((bb * (x + 0.5) * (x + 0.5)) + (aa * (y - 1) * (y - 1)) - (aa * bb) + 0.5);

            while (y > 0)
            {
                y--;
                fy -= aa2;

                if (p >= 0) p += (aa - fy);

                else
                {
                    x++;
                    fx += bb2;
                    p += (fx + aa - fy);
                }

                image[(int)(centerX + x), (int)(centerY + y)] = color;
                image[(int)(centerX + x), (int)(centerY - y)] = color;
                image[(int)(centerX - x), (int)(centerY - y)] = color;
                image[(int)(centerX - x), (int)(centerY + y)] = color;
            }
        }

Source -> http://www.dailyfreecode.com/code/fill-circle-scan-line-circle-fill-675.aspx

/// <summary>
        /// Fills a circle.
        /// </summary>
        /// <param name="image">
        /// The destination image.
        /// </param>
        /// <param name="centerX">
        /// The x center position of the circle.
        /// </param>
        /// <param name="centerY">
        /// The y center position of the circle.
        /// </param>
        /// <param name="radius">
        /// The radius of the circle.
        /// </param>  
        /// <param name="color">
        /// The color to use.
        /// </param>    
        public static void FillCircle<T>(this GenericImage<T> image, int centerX, int centerY, int radius, T color)
        {
            // source -> http://www.dailyfreecode.com/code/fill-circle-scan-line-circle-fill-675.aspx
            int x1;
            int x2;

            var counter = (centerY + radius);

            for (var count = (centerY - radius); count <= counter; count++)
            {
                x1 = (int)(centerX + Math.Sqrt((radius * radius) - ((count - centerY) * (count - centerY))) + 0.5);
                x2 = (int)(centerX - Math.Sqrt((radius * radius) - ((count - centerY) * (count - centerY))) + 0.5);

                image.DrawLine(x1, count, x2, count, color);
            }
        }

Source (converted from Java) -> http://rosettacode.org/wiki/Bitmap/Midpoint_circle_algorithm#Java

/// <summary>
        /// Draws a circle.
        /// </summary>
        /// <param name="image">
        /// The destination image.
        /// </param>
        /// <param name="centerX">
        /// The x center position of the circle.
        /// </param>
        /// <param name="centerY">
        /// The y center position of the circle.
        /// </param>
        /// <param name="radius">
        /// The radius of the circle.
        /// </param>  
        /// <param name="color">
        /// The color to use.
        /// </param>    
        public static void DrawCircle<T>(this GenericImage<T> image, int centerX, int centerY, int radius, T color)
        {
            // source (converted from Java) -> http://rosettacode.org/wiki/Bitmap/Midpoint_circle_algorithm#Java
            var d = (5 - radius * 4) / 4;
            var x = 0;
            var y = radius;

            do
            {
                // ensure index is in range before setting (depends on your image implementation)
                // in this case we check if the pixel location is within the bounds of the image before setting the pixel
                image[centerX + x, centerY + y] = color;
                image[centerX + x, centerY - y] = color;
                image[centerX - x, centerY + y] = color;
                image[centerX - x, centerY - y] = color;
                image[centerX + y, centerY + x] = color;
                image[centerX + y, centerY - x] = color;
                image[centerX - y, centerY + x] = color;
                image[centerX - y, centerY - x] = color;
                if (d < 0)
                {
                    d += 2 * x + 1;
                }
                else
                {
                    d += 2 * (x - y) + 1;
                    y--;
                }
                x++;
            } while (x <= y);
        }

Source (converted from C) -> http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#C

/// <summary>
        /// Draws a line on an <see cref="GenericImage{T}"/>.
        /// </summary>
        /// <param name="image">
        /// The destination image.
        /// </param>
        /// <param name="x1">
        /// The x position for the start of the line.
        /// </param>
        /// <param name="y1">
        /// The y position for the start of the line.
        /// </param>
        /// <param name="x2">
        /// The x position for the end of the line.
        /// </param>
        /// <param name="y2">
        /// The y position for the end of the line.
        /// </param>
        /// <param name="color">
        /// The color that the line will be drawn with.
        /// </param>
        public static void DrawLine<T>(this GenericImage<T> image, int x1, int y1, int x2, int y2, T color)
        {
            // source (converted from C) -> http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#C
            int dx = Math.Abs(x2 - x1), sx = x1 < x2 ? 1 : -1;
            int dy = Math.Abs(y2 - y1), sy = y1 < y2 ? 1 : -1;
            int err = (dx > dy ? dx : -dy) / 2;

            for (; ; )
            {
                image[x1, y1] = color;
                if (x1 == x2 && y1 == y2) break;
                int e2 = err;
                if (e2 > -dx) { err -= dy; x1 += sx; }
                if (e2 < dy) { err += dx; y1 += sy; }
            }
        }

    using System;
    using System.Collections.Generic;

    /// <summary>
    /// Implements a generic equality comparer that uses a callback to perform the comparison.
    /// </summary>
    /// <typeparam name="T">The type we want to compare.</typeparam>
    public class EqualityComparerCallback<T> : IEqualityComparer<T>
    {
        /// <summary>
        /// Holds a reference to the callback that handles comparisons.
        /// </summary>
        private readonly Func<T, T, bool> function;

        /// <summary>
        /// Holds a reference to the callback used to calculate hash codes.
        /// </summary>
        private Func<T, int> hashFunction;
      
        /// <summary>
        /// Initializes a new instance of the <see cref="EqualityComparerCallback{T}"/> class.
        /// </summary>
        /// <param name="func">
        /// The callback function that will do the comparing.
        /// </param>
        /// <exception cref="ArgumentNullException">
        /// Throws a <see cref="ArgumentNullException"/> if the <see cref="func"/> parameter is null.
        /// </exception>
        public EqualityComparerCallback(Func<T, T, bool> func)
        {
            if (func == null)
            {
                throw new ArgumentNullException("func");
            }

            this.function = func;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="EqualityComparerCallback{T}"/> class.
        /// </summary>
        /// <param name="func">
        /// The callback function that will do the comparing.
        /// </param>
        /// <param name="hash">
        /// The callback function that will return the hash code.
        /// </param>  
        public EqualityComparerCallback(Func<T, T, bool> func, Func<T, int> hash)
            : this(func)
        {
            this.hashFunction = hash;
        }

        /// <summary>
        /// Gets or sets the callback function to use to compute the hash.
        /// </summary>
        public Func<T, int> HashFunction
        {
            get
            {
                return this.hashFunction;
            }

            set
            {
                this.hashFunction = value;
            }
        }
                  
        /// <summary>
        /// Provides a static method for returning a <see cref="EqualityComparerCallback{T}"/> type.
        /// </summary>
        /// <param name="func">
        /// The callback function that will do the comparing.
        /// </param>
        /// <returns>Returns a new instance of a <see cref="EqualityComparerCallback{T}"/> type.</returns>
        public static IEqualityComparer<T> Compare(Func<T, T, bool> func)
        {
            return new EqualityComparerCallback<T>(func);
        }

        /// <summary>
        /// Determines whether the specified object instances are considered equal.
        /// </summary>
        /// <param name="x">The first object to compare.</param>
        /// <param name="y">The second object to compare.</param>
        /// <returns>True if the objects are considered equal otherwise, false. If both objA and objB are null, the method returns true.</returns>
        public bool Equals(T x, T y)
        {
            return this.function(x, y);
        }    

        /// <summary>
        /// The get hash code for a object.
        /// </summary>
        /// <param name="obj">
        /// The object whose hash code will be computed.          
        /// </param>
        /// <returns>
        /// Returns a <see cref="int"/> value representing the hash code.
        /// </returns>
        /// <remarks>If no callback function was set for the <see cref="HashFunction"/> the object default <see cref="GetHashCode"/> method will be used.</remarks>
        public int GetHashCode(T obj)
        {
            if (this.hashFunction == null)
            {
                return obj.GetHashCode();
            }

            return this.hashFunction(obj);
        }
    }

A usage scenario

    // build a list of unique categories
    var list = new List<string>();
    foreach (var rule in this.rules)
    {
        if (string.IsNullOrEmpty(rule.Category ?? string.Empty))
        {
            continue;
        }

        // check if already exists
        if (list.Contains(rule.Category, new EqualityComparerCallback<string>((a, b) => a.Trim() == b.Trim())))
        {
            continue;
        }
    }
    return list.ToArray();

Simple solution to get a MIME type from a file extension. Source –> http://stackoverflow.com/a/7161265/341706

public static class MIMEAssistant
{
  private static readonly Dictionary<string, string> MIMETypesDictionary = new Dictionary<string, string>
  {
    {"ai", "application/postscript"},
    {"aif", "audio/x-aiff"},
    {"aifc", "audio/x-aiff"},
    {"aiff", "audio/x-aiff"},
    {"asc", "text/plain"},
    {"atom", "application/atom+xml"},
    {"au", "audio/basic"},
    {"avi", "video/x-msvideo"},
    {"bcpio", "application/x-bcpio"},
    {"bin", "application/octet-stream"},
    {"bmp", "image/bmp"},
    {"cdf", "application/x-netcdf"},
    {"cgm", "image/cgm"},
    {"class", "application/octet-stream"},
    {"cpio", "application/x-cpio"},
    {"cpt", "application/mac-compactpro"},
    {"csh", "application/x-csh"},
    {"css", "text/css"},
    {"dcr", "application/x-director"},
    {"dif", "video/x-dv"},
    {"dir", "application/x-director"},
    {"djv", "image/vnd.djvu"},
    {"djvu", "image/vnd.djvu"},
    {"dll", "application/octet-stream"},
    {"dmg", "application/octet-stream"},
    {"dms", "application/octet-stream"},
    {"doc", "application/msword"},
    {"docx","application/vnd.openxmlformats-officedocument.wordprocessingml.document"},
    {"dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template"},
    {"docm","application/vnd.ms-word.document.macroEnabled.12"},
    {"dotm","application/vnd.ms-word.template.macroEnabled.12"},
    {"dtd", "application/xml-dtd"},
    {"dv", "video/x-dv"},
    {"dvi", "application/x-dvi"},
    {"dxr", "application/x-director"},
    {"eps", "application/postscript"},
    {"etx", "text/x-setext"},
    {"exe", "application/octet-stream"},
    {"ez", "application/andrew-inset"},
    {"gif", "image/gif"},
    {"gram", "application/srgs"},
    {"grxml", "application/srgs+xml"},
    {"gtar", "application/x-gtar"},
    {"hdf", "application/x-hdf"},
    {"hqx", "application/mac-binhex40"},
    {"htm", "text/html"},
    {"html", "text/html"},
    {"ice", "x-conference/x-cooltalk"},
    {"ico", "image/x-icon"},
    {"ics", "text/calendar"},
    {"ief", "image/ief"},
    {"ifb", "text/calendar"},
    {"iges", "model/iges"},
    {"igs", "model/iges"},
    {"jnlp", "application/x-java-jnlp-file"},
    {"jp2", "image/jp2"},
    {"jpe", "image/jpeg"},
    {"jpeg", "image/jpeg"},
    {"jpg", "image/jpeg"},
    {"js", "application/x-javascript"},
    {"kar", "audio/midi"},
    {"latex", "application/x-latex"},
    {"lha", "application/octet-stream"},
    {"lzh", "application/octet-stream"},
    {"m3u", "audio/x-mpegurl"},
    {"m4a", "audio/mp4a-latm"},
    {"m4b", "audio/mp4a-latm"},
    {"m4p", "audio/mp4a-latm"},
    {"m4u", "video/vnd.mpegurl"},
    {"m4v", "video/x-m4v"},
    {"mac", "image/x-macpaint"},
    {"man", "application/x-troff-man"},
    {"mathml", "application/mathml+xml"},
    {"me", "application/x-troff-me"},
    {"mesh", "model/mesh"},
    {"mid", "audio/midi"},
    {"midi", "audio/midi"},
    {"mif", "application/vnd.mif"},
    {"mov", "video/quicktime"},
    {"movie", "video/x-sgi-movie"},
    {"mp2", "audio/mpeg"},
    {"mp3", "audio/mpeg"},
    {"mp4", "video/mp4"},
    {"mpe", "video/mpeg"},
    {"mpeg", "video/mpeg"},
    {"mpg", "video/mpeg"},
    {"mpga", "audio/mpeg"},
    {"ms", "application/x-troff-ms"},
    {"msh", "model/mesh"},
    {"mxu", "video/vnd.mpegurl"},
    {"nc", "application/x-netcdf"},
    {"oda", "application/oda"},
    {"ogg", "application/ogg"},
    {"pbm", "image/x-portable-bitmap"},
    {"pct", "image/pict"},
    {"pdb", "chemical/x-pdb"},
    {"pdf", "application/pdf"},
    {"pgm", "image/x-portable-graymap"},
    {"pgn", "application/x-chess-pgn"},
    {"pic", "image/pict"},
    {"pict", "image/pict"},
    {"png", "image/png"}, 
    {"pnm", "image/x-portable-anymap"},
    {"pnt", "image/x-macpaint"},
    {"pntg", "image/x-macpaint"},
    {"ppm", "image/x-portable-pixmap"},
    {"ppt", "application/vnd.ms-powerpoint"},
    {"pptx","application/vnd.openxmlformats-officedocument.presentationml.presentation"},
    {"potx","application/vnd.openxmlformats-officedocument.presentationml.template"},
    {"ppsx","application/vnd.openxmlformats-officedocument.presentationml.slideshow"},
    {"ppam","application/vnd.ms-powerpoint.addin.macroEnabled.12"},
    {"pptm","application/vnd.ms-powerpoint.presentation.macroEnabled.12"},
    {"potm","application/vnd.ms-powerpoint.template.macroEnabled.12"},
    {"ppsm","application/vnd.ms-powerpoint.slideshow.macroEnabled.12"},
    {"ps", "application/postscript"},
    {"qt", "video/quicktime"},
    {"qti", "image/x-quicktime"},
    {"qtif", "image/x-quicktime"},
    {"ra", "audio/x-pn-realaudio"},
    {"ram", "audio/x-pn-realaudio"},
    {"ras", "image/x-cmu-raster"},
    {"rdf", "application/rdf+xml"},
    {"rgb", "image/x-rgb"},
    {"rm", "application/vnd.rn-realmedia"},
    {"roff", "application/x-troff"},
    {"rtf", "text/rtf"},
    {"rtx", "text/richtext"},
    {"sgm", "text/sgml"},
    {"sgml", "text/sgml"},
    {"sh", "application/x-sh"},
    {"shar", "application/x-shar"},
    {"silo", "model/mesh"},
    {"sit", "application/x-stuffit"},
    {"skd", "application/x-koan"},
    {"skm", "application/x-koan"},
    {"skp", "application/x-koan"},
    {"skt", "application/x-koan"},
    {"smi", "application/smil"},
    {"smil", "application/smil"},
    {"snd", "audio/basic"},
    {"so", "application/octet-stream"},
    {"spl", "application/x-futuresplash"},
    {"src", "application/x-wais-source"},
    {"sv4cpio", "application/x-sv4cpio"},
    {"sv4crc", "application/x-sv4crc"},
    {"svg", "image/svg+xml"},
    {"swf", "application/x-shockwave-flash"},
    {"t", "application/x-troff"},
    {"tar", "application/x-tar"},
    {"tcl", "application/x-tcl"},
    {"tex", "application/x-tex"},
    {"texi", "application/x-texinfo"},
    {"texinfo", "application/x-texinfo"},
    {"tif", "image/tiff"},
    {"tiff", "image/tiff"},
    {"tr", "application/x-troff"},
    {"tsv", "text/tab-separated-values"},
    {"txt", "text/plain"},
    {"ustar", "application/x-ustar"},
    {"vcd", "application/x-cdlink"},
    {"vrml", "model/vrml"},
    {"vxml", "application/voicexml+xml"},
    {"wav", "audio/x-wav"},
    {"wbmp", "image/vnd.wap.wbmp"},
    {"wbmxl", "application/vnd.wap.wbxml"},
    {"wml", "text/vnd.wap.wml"},
    {"wmlc", "application/vnd.wap.wmlc"},
    {"wmls", "text/vnd.wap.wmlscript"},
    {"wmlsc", "application/vnd.wap.wmlscriptc"},
    {"wrl", "model/vrml"},
    {"xbm", "image/x-xbitmap"},
    {"xht", "application/xhtml+xml"},
    {"xhtml", "application/xhtml+xml"},
    {"xls", "application/vnd.ms-excel"},                        
    {"xml", "application/xml"},
    {"xpm", "image/x-xpixmap"},
    {"xsl", "application/xml"},
    {"xlsx","application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
    {"xltx","application/vnd.openxmlformats-officedocument.spreadsheetml.template"},
    {"xlsm","application/vnd.ms-excel.sheet.macroEnabled.12"},
    {"xltm","application/vnd.ms-excel.template.macroEnabled.12"},
    {"xlam","application/vnd.ms-excel.addin.macroEnabled.12"},
    {"xlsb","application/vnd.ms-excel.sheet.binary.macroEnabled.12"},
    {"xslt", "application/xslt+xml"},
    {"xul", "application/vnd.mozilla.xul+xml"},
    {"xwd", "image/x-xwindowdump"},
    {"xyz", "chemical/x-xyz"},
    {"zip", "application/zip"}
  };

  public static string GetMIMEType(string fileName)
  {
    if (Path.GetExtension(fileName).Length > 1 && MIMETypesDictionary.ContainsKey(Path.GetExtension(fileName).Remove(0, 1)))
    {
      return MIMETypesDictionary[Path.GetExtension(fileName).Remove(0, 1)];
    }
    return "unknown/unknown";
  }
}

I needed a quick file caching solution and here is what I came up with …

    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Text;

    /// <summary>
    /// Provides a file model used by the <see cref="FileCache"/> type.
    /// </summary>
    public class FileModel
    {
        /// <summary>
        /// Gets or sets information about the file.
        /// </summary>
        public FileInfo Info { get; set; }

        /// <summary>
        /// Gets or sets the last time that the file had it's contents cached.
        /// </summary>
        public DateTime LastUpdate { get; set; }

        /// <summary>
        /// Gets or sets the file content for the file.
        /// </summary>
        public StringBuilder  Data { get; set; }
    }

    /// <summary>
    /// Provides a caching for file content based on file extensions.
    /// </summary>
    public class FileCache
    {
        /// <summary>
        /// Holds a singleton instance of a <see cref="FileCache"/> type.
        /// </summary>
        private static FileCache singleton;

        /// <summary>
        /// Used to hold the contents of the files.
        /// </summary>
        private readonly Dictionary<string, FileModel> files;

        /// <summary>
        /// Holds the list of extensions for files that will have there contents cached.
        /// </summary>
        private readonly List<string> extensions;

        /// <summary>
        /// Gets or sets a time value used to determine if a files content should be read again.
        /// </summary>
        public TimeSpan CacheTime { get; set; }

        /// <summary>
        /// Gets a list of file extension that will have there contents cached.
        /// </summary>
        public List<string> Extensions
        {
            get
            {
                return this.extensions;
            }
        }

        /// <summary>
        /// Default constructor.
        /// </summary>
        public FileCache()
        {
            this.files = new Dictionary<string, FileModel>();
            this.extensions = new List<string>();
            this.extensions.AddRange(new[] { ".htm" });
            this.CacheTime = TimeSpan.FromSeconds(2);
        }

        /// <summary>
        /// Provides a helper method for retrieving a file.
        /// </summary>
        /// <param name="path">The path to the file.</param>
        /// <returns>Returns a <see cref="FileModel"/> type containing information about the file.</returns>
        public static FileModel GetFile(string path)
        {
            return Instance.Get(path);
        }

        /// <summary>
        /// Provides a helper method for retrieving a file.
        /// </summary>
        /// <param name="path">The path to the file.</param>
        /// <returns>Returns a <see cref="FileModel"/> type containing information about the file.</returns>
        public FileModel Get(string path)
        {
            // if file does not exit just return null
            if (!File.Exists(path))
            {
                return null;
            }

            // check if file already exists in the cache
            FileModel model;
            if (this.files.ContainsKey(path))
            {
                // get existing entry
                model = this.files[path];
            }
            else
            {
                // add new entry
                model = new FileModel { LastUpdate = DateTime.Now, Info = new FileInfo(path) };
                this.files.Add(path, model);
            }

            // check to cache file data
            if (this.extensions.Contains(model.Info.Extension))
            {
                // not data has been read yet OR (the current time has surpassed the last update time plus the cache time AND 
                // the current time is greater then the last write time  ) we can read the contents of the file
                if (model.Data == null || (DateTime.Now > model.LastUpdate + this.CacheTime && DateTime.Now > model.Info.LastWriteTime))
                {
                    model.Data = new StringBuilder(File.ReadAllText(model.Info.FullName));
                }
            }

            // return the modal data
            return model;
        }

        /// <summary>
        /// Gets a singleton instance of a <see cref="FileCache"/> type.
        /// </summary>
        public static FileCache Instance
        {
            get
            {
                return singleton ?? (singleton = new FileCache());
            }
        }
    }

MEFHelpers provides a helper class that provides a static method to make MEF composition easier.

    /// <summary>
    /// Provides a helper class for MEF composition.
    /// </summary>
    public sealed class MEFHelpers
    {
        /// <summary>
        /// Composes MEF parts.
        /// </summary>
        /// <param name="parts">The composable object parts.</param>
        public static void Compose(params object[] parts)
        {
            Compose(parts, new string[0]);
        }

        /// <summary>
        /// Composes MEF parts.
        /// </summary>
        /// <param name="searchFolders">Provides a series of search folders to search for *.dll files.</param>
        /// <param name="parts">The composable object parts.</param>
        public static void Compose(IEnumerable<string> searchFolders, params object[] parts)
        {
            // setup composition container
            var catalog = new AggregateCatalog();

            // check if folders were specified
            if (searchFolders != null)
            {
                // add search folders
                foreach (var folder in searchFolders.Where(System.IO.Directory.Exists))
                {
                    catalog.Catalogs.Add(new DirectoryCatalog(folder, "*.dll"));
                }
            }

            // compose and create plug ins
            var composer = new CompositionContainer(catalog);
            composer.ComposeParts(parts);
        }
    }

A usage scenario is provided below

    public class KissCSMEFComposer  
    {
        [ImportMany(typeof(IProcessor))]
        public List<Lazy<IProcessor>> StringProcessors;

        [ImportMany(typeof(ICommandRepository))]
        public List<Lazy<ICommandRepository>> CommandRepository;
    }

    var composer = new KissCSMEFComposer();
    // try to connect with MEF types
    try
    {
        MEFHelpers.Compose(this.SearchFolders, composer);
    }
    catch (Exception ex)
    {
        // ERR: handle error
    }

    // register string processors
    foreach (var processor in composer.StringProcessors)
    {
        StringProcessorRepository.Instance.Register(processor.Value);
    }

    // etc ...

The code below can be used to log performance of your code.

    using System.Collections.Generic;
    using System.Diagnostics;

    /// <summary>
    /// Provides a simple performance testing class that utilizes <see cref="Stopwatch"/>.
    /// </summary>
    /// <typeparam name="T">The type that will be used as the indexer.</typeparam>
    public class PerformanceTesting<T>
    {
        /// <summary>
        /// Provides a model that contains timer information.
        /// </summary>
        private class TimerModel
        {
            /// <summary>
            /// Used to record performance timings.
            /// </summary>
            public readonly Stopwatch Timer;

            /// <summary>
            /// Used to record how many times the <see cref="Timer"/> has been started.
            /// </summary>
            public int Count;

            /// <summary>
            /// Used to store the enabled state.
            /// </summary>
            private bool enabled;

            /// <summary>
            /// Gets or sets a value whether or not this timer if enabled.
            /// </summary>
            /// <remarks>If <see cref="Timer"/> has been started and Enabled is set to false the timer will be stopped.</remarks>
            public bool Enabled
            {
                get
                {
                    return this.enabled;
                }

                set
                {
                    this.enabled = value;

                    // be sure to stop the timer if disabled
                    if (!value && this.Timer.IsRunning)
                    {
                        this.Timer.Stop();
                    }
                }
            }

            /// <summary>
            /// Default constructor.
            /// </summary>
            public TimerModel()
            {
                this.Timer = new Stopwatch();
                this.enabled = true;
            }
        }

        /// <summary>
        /// Holds a reference to a singleton instance.
        /// </summary>
        private static PerformanceTesting<T> singleton;

        /// <summary>
        /// Used to store various timer information.
        /// </summary>
        private readonly Dictionary<T, TimerModel> timers;

        /// <summary>
        /// Default constructor.
        /// </summary>
        public PerformanceTesting()
        {
            this.timers = new Dictionary<T, TimerModel>();
        }

        /// <summary>
        /// Creates a new timer.
        /// </summary>
        /// <param name="key">The unique key for the timer.</param>
        /// <remarks>It is best to create the timer at the start of the application getting it ready for use.</remarks>
        public void Create(T key)
        {
            this.timers.Add(key, new TimerModel());
        }

        /// <summary>
        /// Creates a new timer for each key.
        /// </summary>
        /// <param name="keys">The unique keys for the timers.</param>
        /// <remarks>It is best to create the timer at the start of the application getting it ready for use.</remarks>
        public void Create(T[] keys)
        {
            foreach (var key in keys)
            {
                this.timers.Add(key, new TimerModel());
            }
        }

        /// <summary>
        /// Returns the total ticks that this timer has observed.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <returns>Returns a time value in ticks.</returns>
        public long TotalTicks(T key)
        {
            var model = this.timers[key];
            return model.Timer.ElapsedTicks;
        }

        /// <summary>
        /// Returns the total ticks that this timer has observed.
        /// </summary>
        /// <param name="keys">The keys to the timers information.</param>
        /// <returns>Returns the sum of the time values in ticks.</returns>
        public long TotalTicks(T[] keys)
        {
            long total = 0;
            foreach (var key in keys)
            {
                var model = this.timers[key];
                total += model.Timer.ElapsedTicks;
            }

            return total;
        }

        /// <summary>
        /// Gets the start count.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <returns>The number of times the timer has started.</returns>
        public int GetStartCount(T key)
        {
            var model = this.timers[key];
            return model.Count;
        }

        /// <summary>
        /// Gets the start count for specified timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <returns>The sum total of times all specified the timers have started.</returns>
        public int GetStartCount(T[] keys)
        {
            int total = 0;
            foreach (var key in keys)
            {
                var model = this.timers[key];
                total += model.Count;
            }

            return total;
        }

        /// <summary>
        /// Returns the total ticks that this timer has observed.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <returns>Returns a time value in milliseconds.</returns>
        public long TotalMilliseconds(T key)
        {
            var model = this.timers[key];
            return model.Timer.ElapsedMilliseconds;
        }

        /// <summary>
        /// Returns the total ticks that this timer has observed.
        /// </summary>
        /// <param name="keys">The keys to the timers information.</param>
        /// <returns>Returns the sum of the time values in milliseconds.</returns>
        public long TotalMilliseconds(T[] keys)
        {
            long total = 0;
            foreach (var key in keys)
            {
                var model = this.timers[key];
                total += model.Timer.ElapsedMilliseconds;
            }

            return total;
        }

        /// <summary>
        /// Calculates the average time in ticks that elapsed while this timer was recording.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <returns>Returns the average time in ticks that elapsed between each start and stop.</returns>
        public long AverageTicks(T key)
        {
            var model = this.timers[key];
            return model.Timer.ElapsedTicks / model.Count;
        }

        /// <summary>
        /// Calculates the total average time in ticks that elapsed while the specified timers were recording.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <returns>Returns the total average time in ticks that elapsed between each start and stop for all the specified timers.</returns>
        public long AverageTicks(T[] keys)
        {
            long total = 0;
            var count = 0;
            foreach (var key in keys)
            {
                var model = this.timers[key];
                total += model.Timer.ElapsedTicks;
                count += model.Count;
            }

            return total / count;
        }

        /// <summary>
        /// Calculates the average time in milliseconds that elapsed while this timer was recording.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <returns>Returns the average time in milliseconds that elapsed between each start and stop.</returns>
        public long AverageMilliseconds(T key)
        {
            var model = this.timers[key];
            if (model.Count == 0)
            {
                return 0;
            }

            return model.Timer.ElapsedMilliseconds / model.Count;
        }

        /// <summary>
        /// Calculates the total average time in milliseconds that elapsed while the specified timers were recording.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <returns>Returns the total average time in milliseconds that elapsed between each start and stop for all the specified timers.</returns>
        public long AverageMilliseconds(T[] keys)
        {
            long total = 0;
            var count = 0;
            foreach (var key in keys)
            {
                var model = this.timers[key];
                total += model.Timer.ElapsedMilliseconds;
                count += model.Count;
            }

            if (count == 0)
            {
                return 0;
            }

            return total / count;
        }

        /// <summary>
        /// Removes the specified timers.
        /// </summary>
        /// <param name="keys">The keys to the timers that will be removed.</param>
        public void Remove(T[] keys)
        {
            foreach (var key in keys)
            {
                this.timers.Remove(key);
            }
        }

        /// <summary>
        /// Removes a timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        public void Remove(T key)
        {
            this.timers.Remove(key);
        }

        /// <summary>
        /// Resets all the timers.
        /// </summary>
        public void ResetAll()
        {
            foreach (var pair in this.timers)
            {
                pair.Value.Timer.Reset();
            }
        }

        /// <summary>
        /// Resets all the timers.
        /// </summary>
        /// <param name="resetCounts">If true will set each timer start count to 0.</param>
        public void ResetAll(bool resetCounts)
        {
            foreach (var pair in this.timers)
            {
                pair.Value.Timer.Reset();
                if (resetCounts)
                {
                    pair.Value.Count = 0;
                }
            }
        }

        /// <summary>
        /// Gets an array of timer keys.
        /// </summary>
        /// <returns>Returns an array of timer keys.</returns>
        public T[] GetKeys()
        {
            var keys = new T[this.timers.Count];
            this.timers.Keys.CopyTo(keys, 0);
            return keys;
        }

        /// <summary>
        /// Sets the enabled state of the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <param name="enabled">If true the timer will be enabled. If false the timer will be stopped if it is running.</param>
        public void SetEnabled(T key, bool enabled)
        {
            var model = this.timers[key];
            model.Enabled = enabled;
        }

        /// <summary>
        /// Sets the enabled state of the specified timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <param name="enabled">If true the timers will be enabled. If false the timers will be stopped if they are running.</param>
        public void SetEnabled(T[] keys, bool enabled)
        {
            foreach (var key in keys)
            {
                var model = this.timers[key];
                model.Enabled = enabled;
            }
        }

        /// <summary>
        /// Gets the enabled state of the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        public bool IsEnabled(T key)
        {
            var model = this.timers[key];
            return model.Enabled;
        }

        /// <summary>
        /// Gets the enabled state of the specified timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <param name="enabled">Will contain the enabled state for each specified key.</param>
        public void IsEnabled(T[] keys, out bool[] enabled)
        {
            var enabledStates = new bool[keys.Length];
            for (int i = 0; i < keys.Length; i++)
            {
                var model = this.timers[keys[i]];
                enabledStates[i] = model.Enabled;
            }

            enabled = enabledStates;
        }

        /// <summary>
        /// Starts the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <remarks>Will not start if the enabled state is false.</remarks>
        public void Start(T key)
        {
            var model = this.timers[key];
            if (!model.Enabled)
            {
                return;
            }
            model.Count++;
            model.Timer.Start();
        }

        /// <summary>
        /// Starts the timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <remarks>Will not start if the timers enabled state is false.</remarks>
        public void Start(T[] keys)
        {
            foreach (var key in keys)
            {
                var model = this.timers[key];
                if (!model.Enabled)
                {
                    continue;
                }
                model.Count++;
                model.Timer.Start();
            }
        }

        /// <summary>
        /// Stops the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        public void Stop(T key)
        {
            var model = this.timers[key];
            if (!model.Enabled)
            {
                return;
            }
            model.Timer.Stop();
        }

        /// <summary>
        /// Stops the timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        public void Stop(T[] keys)
        {
            foreach (var key in keys)
            {
                var model = this.timers[key];
                if (!model.Enabled)
                {
                    continue;
                }
                model.Timer.Stop();
            }
        }

        /// <summary>
        /// Resets the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        public void Reset(T key)
        {
            this.Reset(key, false);
        }

        /// <summary>
        /// Resets the timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        public void Reset(T[] keys)
        {
            this.Reset(keys, false);
        }

        /// <summary>
        /// Resets the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <param name="resetCount">If true the start count for the timer will be set to 0.</param>
        public void Reset(T key, bool resetCount)
        {
            var model = this.timers[key];
            model.Timer.Reset();
            if (resetCount)
            {
                model.Count = 0;
            }
        }

        /// <summary>
        /// Resets the timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <param name="resetCounts">If true the start count for the timers will be set to 0.</param>
        public void Reset(T[] keys, bool resetCounts)
        {
            foreach (var key in keys)
            {
                var model = this.timers[key];
                model.Timer.Reset();
                if (resetCounts)
                {
                    model.Count = 0;
                }
            }
        }

        /// <summary>
        /// Resets the timer start count to 0.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        public void ResetCount(T key)
        {
            var model = this.timers[key];
            model.Count = 0;
        }

        /// <summary>
        /// Resets each timer start count to 0.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        public void ResetCount(T[] keys)
        {
            foreach (var key in keys)
            {
                var model = this.timers[key];
                model.Count = 0;
            }
        }

        /// <summary>
        /// Restarts the timer.
        /// </summary>
        /// <param name="key">The key to the timer information.</param>
        /// <param name="resetCount">If true the start count for the timer will be set to 0.</param>
        /// <remarks>The timer will be reset then started again.</remarks>
        public void Restart(T key, bool resetCount)
        {
            var model = this.timers[key];
            model.Timer.Reset();
            if (resetCount)
            {
                model.Count = 0;
            }

            this.Start(key);
        }

        /// <summary>
        /// Restarts the specified timers.
        /// </summary>
        /// <param name="keys">The keys to the timer information.</param>
        /// <param name="resetCounts">If true the start count for the timers will be set to 0.</param>
        /// <remarks>Each timer will be reset then started again.</remarks>
        public void Restart(T[] keys, bool resetCounts)
        {
            foreach (var key in keys)
            {
                var model = this.timers[key];
                model.Timer.Reset();
                if (resetCounts)
                {
                    model.Count = 0;
                }
            }

            this.Start(keys);
        }

        /// <summary>
        /// Gets a singleton instance of the <see cref="PerformanceTesting{T}"/> class.
        /// </summary>
        public static PerformanceTesting<T> Instance
        {
            get
            {
                return singleton ?? (singleton = new PerformanceTesting<T>());
            }
        }
    }

Setting up a performance counter

#if PERFORMANCE
            var perf = PerformanceTesting<string>.Instance;
            perf.Create("ScanLines");
#endif

A sample usage

#if PERFORMANCE
                var perf = PerformanceTesting<string>.Instance;
                perf.Reset("ScanLines");
                perf.Start("ScanLines");
#endif
                this.scanner.Calculate(this.points);
#if PERFORMANCE
                perf.Stop("ScanLines");
#endif

How to report the results

#if PERFORMANCE
        public static void ReportPerformanceTimes()
        {
            var perf = PerformanceTesting<string>.Instance;
            foreach (var value in perf.GetKeys())
            {
                Debug.Log(string.Format("{0} - Total: {1}ms Average: {2} Count: {3}", value, perf.TotalMilliseconds(value), perf.AverageMilliseconds(value), perf.GetStartCount(value)));
            }

            Debug.Log(string.Format("Total Performance Times - Total: {0}ms", perf.TotalMilliseconds("ScanLines")));
        }
#endif