I downloaded an open source project in ASP.NET language.

And I couldn't find any Codebehind file for example inside the Login.aspx the Codebehind is Login.aspx.cs but I cant find it anywhere in the source file. and the Line Codebehind="Login.aspx.cs" identified as "File Login.aspx.cs was not found" but yet the function is still working.

Where can I access those .cs file?