C# Signature:

[DllImport("shlwapi.dll", CharSet=CharSet.Auto)]
static extern bool PathRelativePathTo(
     [Out] StringBuilder pszPath,
     [In] string pszFrom,
     [In] uint dwAttrFrom,
     [In] string pszTo,
     [In] uint dwAttrTo
);

VB Signature:

<DllImport("shlwapi.dll", CharSet:=CharSet.Auto)> _
Public Shared Function PathRelativePathTo( _
     ByVal pszPath As StringBuilder, _
     ByVal pszFrom As String, _
     ByVal dwAttrFrom As Integer, _
     ByVal pszTo As String, _
     ByVal dwAttrTo As Integer) As Boolean
End Function

User-Defined Types:

None.

Notes:

None.

Tips & Tricks:

The Microsoft.VisualBasic.FileAttribute enumeration can be used to specify the file attribute

Sample Code:

const UInt32 FILE_ATTRIBUTE_DIRECTORY = 0x10;
const Int32 MAX_PATH = 260;
StringBuilder str = new StringBuilder(MAX_PATH);
UInt32 dwAttr1 = FILE_ATTRIBUTE_DIRECTORY;
UInt32 dwAttr2 = 0;
Boolean bRet = PathRelativePathTo(
     str,
     @"c:\a\b\path", dwAttr1,
     @"c:\a\x\y\file", dwAttr2
     );
// Result: str.ToString() == @"..\..\x\y\file"

Alternative Managed API:

Do you know one? Please contribute it!