MetaWebLogger is a .NET C# library that makes it really simple to include in your blog engine so that you can use Windows Live Writer or other blog writing tools that support the MetaWeblog API to write and edit posts in your blogging engine
The library is developed in .NET C# 4
I've written a blog post on my website that explains how you would use this library. I use this library on my on blog as well.
MetaWeblog API C# Library