ASP.Net error: "The type 'foo' exists in both "temp1.dll" and "temp2.dll"

This might happen if you place .cs files in App_Code and changed their build action to compile in a Web Application Project.

Either have the build action for the .cs files in App_Code as Content or change the name of App_Code to something else. I changed the name since intellisense won't fix .cs files marked as content.

More info at http://vishaljoshi.blogspot.se/2009/07/appcode-folder-doesnt-work-with-web.html

One possible reason for this error is that there are 2 aspx pages which are having the same name in their inherits= in the <@page language=......inherits=> line.

Changing the inherits= name solves the error.

Add the batch="false" attribute to the "compilation" element of the web.config file.

This problem occurs because of the way in which ASP.NET 2.0 uses the application references and the folder structure of the application to compile the application. If the batch property of the element in the web.config file for the application is set to true, ASP.NET 2.0 compiles each folder in the application into a separate assembly.

http://www.sellsbrothers.com/1995

http://support.microsoft.com/kb/919284