Full repo available at https://bitbucket.org/createdbyx/codefarts.utilities-extension-methods-only

/// <summary>
/// Moves the specified entries in the array by a set ammount.
/// </summary>
/// <typeparam name="T">Specifies the generic type of the array.</typeparam>
/// <param name="array">The destination array.</param>
/// <param name="index">The start index where entries will be moved from.</param>
/// <param name="length">The number of entries to be moved.</param>
/// <param name="shift">The ammount and direction to move the specified entries.</param>
/// <returns>
/// Returns the resized and updated destination array.
/// </returns>
/// <exception cref="ArgumentOutOfRangeException">length;'length' argument must be greater then 0.</exception>
/// <remarks><p>To move entries to the left (towards 0) specify a negative shift value and a positive shift value to move entries to the right.</p>
/// <example>
/// <code>
/// var items = new[] { 0, 1, 2, 3, 4 };
/// items = items.Move(3, 2, -1);
/// </code>
/// Result should be { 0, 1, 3, 4, 4 }
/// </example></remarks>
public static T[] Move<T>(this T[] array, int index, int length, int shift)
{
    if (length <= 0)
    {
        throw new ArgumentOutOfRangeException("length", "'length' argument must be greater then 0.");
    }

    if (shift > 0 && index + length + shift > array.Length - 1)
    {
        Array.Resize(ref array, array.Length + (index + length + shift - array.Length));
    }

    if (index + shift < 0)
    {
        length += index + shift;
        index = -(index + shift);
    }

    length = Math.Min(array.Length - index, length);
    if (length > 0)
    {
        Array.Copy(array, index, array, index + shift, length);
    }        

    return array;
}