Debugging Class Library

Question

I am having difficulties in debugging a C# class library. I have these following 4 files: 1. ReadFile.cs 2. MainClass.cs 3. File1.dll 4. File2.exe ReadFile.cs is the source for File1.dll library. MainClass.cs is the source for File2.exe executable, which reference the File1.dll. There is no project file (i.e. .csproj file) at all. My objective is to debug (set a breakpoint, etc) the ReadFile.cs. Can anybody please help? Thanks.