Compilation error by registering of the custom web part

Problem Description:

By implementing of custom web parts based on ASP.NET 2.0, you will probably find many examples, which simple do not work.

One of common problems is that the custom web part is not properly registered in the parent page.

For example, image you implemented the web part in the namespace TextDisplayWebPart. Usually, the web part should be registered at the parent page as shown here:

<%@ Register TagPrefix="part"  Namespace="DaenetGadgetTestWebApplication" %>

Unofortinately, after build process you will get fillowing error:

“Element 'TextDisplayWebPart' is not a known element. This can occur if there is a compilation error in the Web site.”

Solution:

Solution in this case is more than simple. By registering of the web part in the previous example, the assembly directive is missing:

<%@ Register TagPrefix="part" Assembly="GadgetTestWebApplication" Namespace="GadgetTestWebApplication" %>