I recently came across a strange behavior while loading text resource assets. In particular the Resources.LoadAll method does not accept Path.DirectorySeparatorChar characters in a path. In fact it only accepts Path.AltDirectorySeparatorChar characters. This behavior is different then standard .net file/folder methods that accept either Path.AltDirectorySeparatorChar or Path.DirectorySeparatorChar without distinction. What this means is that you can’t directly use Path.Combine to build a path and pass it to the Resources.LoadAll method you first have to replace any Path.DirectorySeparatorChar characters with Path.AltDirectorySeparatorChar characters.

The documentation for Resources.Load also does not mention this behavior.

I have submitted a bug report here –> https://fogbugz.unity3d.com/default.asp?533268_jgvrk2lbu1qm398e

    using System.IO;

    using UnityEditor;

    using UnityEngine;

    /// <summary>
    /// Handles settings registration.
    /// </summary>
    [InitializeOnLoad]
    public class EditorInitialization
    {
        /// <summary>
        /// Holds a value indicating whether the RunCallbacks method has been called at least once before.
        /// </summary>
        private static bool ranOnce;

        /// <summary>
        /// Initializes static members of the <see cref="EditorInitialization"/> class.
        /// </summary>
        static EditorInitialization()
        {
            EditorApplication.update += RunCallbacks;
        }

        private static void RunCallbacks()
        {
            if (!ranOnce)
            {
                // try to load resource
                var path = Path.Combine("Test/SubFolder", "testfile"); // result is Test/SubFolder\testfile

                // var data = Resources.LoadAll("Test/SubFolder/testfile", typeof(TextAsset)); // this line is successful
                var data = Resources.LoadAll(path, typeof(TextAsset));  // this line fails

                if (data != null && data.Length != 0)
                {
                    Debug.Log("found it");
                }
                else
                {
                    Debug.Log("not found! " + path);
                }

                ranOnce = true;
                return;
            }

            // do stuff 
        }
    }