如何扩展msbuild以在.cs文件上运行自定义预处理器？

I have a custom program which preprocesses a C# file and generates a new C# file as output. I would like to invoke this from msbuild on each of the C# files in the project, then compile the output files instead of the original C# files. How would I go about this?I have a custom program which preprocesses a C#