So I am a newbie and I couldn't find a proper answer to this on the internet. After digging a little bit here is what I came up with.
Download google-diff-match-patch from here
One you have extracted it, open up your microsoft visual studio project
Go to View->Solution Explorer or press Ctrl+Alt+L
In solution Explorer right click on your project name and go to Add->Existing Item... or press Shift+Alt+A
In the dialog box that appears locate your diff-match-patch folder and go in csharp directory and select DiffMatchPatch.cs and click on Add
Then in solution explorer right click on References->Add Reference...
Search for System.Web and add it.
Now come back to your program (in my case Form1.cs) and type
using DiffMatchPatch;
Now you are ready to use all the functions of the diff-match-patch library in your C# program