Added relativepathfinderhelper

DeveCoolLib.Tests/PathHelpers/RelativePathFinderHelperTests.cs

@@ -0,0 +1,51 @@
+using DeveCoolLib.PathHelpers;
+using System;
+using Xunit;
+
+namespace DeveCoolLib.Tests.PathHelpers
+{
+    public class RelativePathFinderHelperTests
+    {
+        [Fact]
+        public void MakesARelativePath()
+        {
+            string dirPath;
+            string filePath;
+            if (OperatingSystem.IsWindows())
+            {
+                dirPath = @"C:\WOP\DeveMazeGenerator";
+                filePath = @"C:\WOP\DevemazeGenerator\Images\TestImage.png";
+            }
+            else
+            {
+                dirPath = @"/home/WOP/DeveMazeGenerator";
+                filePath = @"/home/WOP/DeveMazeGenerator/Images/TestImage.png";
+            }
+
+            var expectedPath = @"Images/TestImage.png";
+
+            var relativePath = RelativePathFinderHelper.GetRelativePath(dirPath, filePath);
+            Assert.Equal(expectedPath, relativePath);
+        }
+
+        [Fact]
+        public void WorksForNullPath()
+        {
+            string dirPath = null;
+            string filePath;
+            if (OperatingSystem.IsWindows())
+            {
+                filePath = @"C:\WOP\DevemazeGenerator\Images\TestImage.png";
+            }
+            else
+            {
+                filePath = @"/home/WOP/DeveMazeGenerator/Images/TestImage.png";
+            }
+
+            var expectedPath = filePath;
+
+            var relativePath = RelativePathFinderHelper.GetRelativePath(dirPath, filePath);
+            Assert.Equal(expectedPath, relativePath);
+        }
+    }
+}

DeveCoolLib/Collections/EqualityComparerFactory.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 
-namespace DeveCoolLib
+namespace DeveCoolLib.Collections
 {
     /// <summary>
     /// Utility class for creating <see cref="IEqualityComparer{T}"/> instances 

DeveCoolLib/PathHelpers/RelativePathFinderHelper.cs

@@ -0,0 +1,46 @@
+using System;
+using System.IO;
+
+namespace DeveCoolLib.PathHelpers
+{
+    public static class RelativePathFinderHelper
+    {
+        public static string GetRelativePath(string originDirectory, string fullPathOfFile)
+        {
+            return GetRelativePath(originDirectory != null ? new DirectoryInfo(originDirectory) : null, fullPathOfFile != null ? new FileInfo(fullPathOfFile) : null);
+        }
+
+        public static string GetRelativePath(FileSystemInfo? destinationPath, FileSystemInfo? originPath)
+        {
+            if (originPath == null)
+            {
+                throw new ArgumentNullException(nameof(originPath));
+            }
+
+            if (destinationPath == null)
+            {
+                return originPath.FullName;
+            }
+
+            string path1FullName = GetFullName(destinationPath);
+            string path2FullName = GetFullName(originPath);
+
+            Uri uri1 = new Uri(path1FullName);
+            Uri uri2 = new Uri(path2FullName);
+            Uri relativeUri = uri1.MakeRelativeUri(uri2);
+
+            return relativeUri.OriginalString;
+        }
+
+        private static string GetFullName(FileSystemInfo path)
+        {
+            string fullName = path.FullName;
+
+            if (path is DirectoryInfo && fullName[fullName.Length - 1] != Path.DirectorySeparatorChar)
+            {
+                fullName += Path.DirectorySeparatorChar;
+            }
+            return fullName;
+        }
+    }
+}