如何在项目中使用不同的文件以用于不同的构建配置 - Visual Studio C＃.net

I have a c# .net winforms solution and I want to create two different builds: one that supports IE6 and one that supports IE7. A few of the files in one of my projects are different for the IE6 build versus the IE7 build, so I want to include the IE6 files when I build for IE6 and the IE7 files when I build for IE7. What's the best way of structuring my solution for this situation?I have a c# .net winforms solution and I want t