File or assembly name Microsoft.Web.UI.WebControls, or one of its dependencies, was not found.
Error found in Line 2:
<%@ Register TagPrefix="mytree" Namespace="Microsoft.Web.UI.WebControls">
So it can't find the Web control DLL's I assume. What am I doing wrong?
I don't see your Assembly attribute. It's required in order to locate the assembly where the control lives. If that doesn't solve the problem (or if you're already putting that in place), try manually adding the assembly to the GAC, using the .NET Framework configuration tool (inside Administrative Tools). Select Manage the Assembly Cache, then the Add an Assembly to the Assembly Cache. Locate the webcontrols DLL and that should do the trick.
This was first published in August 2003