While working on my first project with Visual Studio 2010, i had to go through some weird stuffs as I tried to convert a Website project to a Website Application project.

One of the problems was with custom controls.
Here is the sample code in C# of a custom control I used for that project.

namespace CustomControls
{
public class MyTextArea : TextBox
{
//———-code here
}
}

On web.cinfig I added

On a page I use the control like this:

It compiles fine without any error. However when I view the page on browser I get the error:
Unknown Server Tag cc:MyTextArea

Note that this code worked fine in both visual studio 2005, and visual studio 2008.

Solution:
Apparently I would need to add the assembly reference on web.config

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