Error occurred during the processing of . Could not load the assembly

An error occurred during the processing of . Could not load the assembly 'SharePointCodeBehindDemo, Version=1.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'. Make sure that it is compiled before accessing the page. 

Solution :

This is the [Namespace].[ClassName],[AssemblyName] syntax that I am assuming you put in the inherit's attribute in your ASPX.