LemmaGenerator creates lemmatizers for several European languages that you can customize.

This project was created by Matjaz Jursic and was retrieved on http://lemmatise.ijs.si/. He's the expert and did a great job so for all questions you should check his website.

I just added this project to git to be able to fork it. In particular, I created the associated nuget package available at http://www.nuget.org/packages/LemmaGenerator/

If you just want to lemmatize words, you want to check the precompiled lemmatizer files here: https://github.com/AlexPoint/LemmaGenerator/tree/master/Test/Data.

Load the selected file in a stream a build a lemmatizer with it:

var path = "/path/to/the/lemmatizer/file";
var stream = File.OpenRead(dataFilePath);
var lemmatizer = new Lemmatizer(stream);
var result = lemmatizer.Lemmatize("words");
Console.WriteLine(result);
// prints "word"

As mentioned above, you can customize your lemmatizer by using your own dictionary { word, lemma }.

For more information, check Matjaz's website http://lemmatise.ijs.si/.