How do I get a relative path from one path to another in C# [duplicate]

Question

I'm hoping there is a built in .NET method to do this, but I'm not finding it.

I have two paths that I know to be on the same root drive, I want to be able to get a relative path from one to the other.

string path1 = @"c:\dir1\dir2\";
string path2 = @"c:\dir1\dir3\file1.txt";
string relPath = MysteryFunctionThatShouldExist(path1, path2); 
// relPath == "..\dir3\file1.txt"

Does this function exist? If not what would be the best way to implement it?

Answer 1

Uri works:

Uri path1 = new Uri(@"c:\dir1\dir2\");
Uri path2 = new Uri(@"c:\dir1\dir3\file1.txt");
Uri diff = path1.MakeRelativeUri(path2);
string relPath = diff.OriginalString;

Answer 2

You could also import the PathRelativePathTo function and call it.

e.g.:

using System.Runtime.InteropServices;

public static class Util
{
  [DllImport( "shlwapi.dll", EntryPoint = "PathRelativePathTo" )]
  protected static extern bool PathRelativePathTo( StringBuilder lpszDst,
      string from, UInt32 attrFrom,
      string to, UInt32 attrTo );

  public static string GetRelativePath( string from, string to )
  {
    StringBuilder builder = new StringBuilder( 1024 );
    bool result = PathRelativePathTo( builder, from, 0, to, 0 );
    return builder.ToString();
  }
}