OatmealDome.UnifiedDiff
This library allows you to create unified diff files for use with patch. Note that this library does not aim to duplicate the exact output from diff.
Usage
string alphaText = File.ReadAllText("a.txt");
string bravoText = File.ReadAllText("b.txt");
UnifiedDiffFile unifiedDiff = UnifiedDiffFile.Create(alphaText, bravoText);
File.WriteAllText("output.patch", unifiedDiff.ToString());