For compiler error information: the supplementary question of cs1595 has defined "customcontrols. firstcontrol" in multiple places"

"Mmcontrols. firstcontrol" has been defined in multiple places

It is estimated that you have repeated or old assemblies. Delete the DLLs in the bin and re-compile it. For the sake of peace of mind, delete it at the same time. <br>

C: \ windows \ Microsoft. NET \ framework \ v1.1.4322 \ temporary & nbsp; ASP. NET & nbsp; Files <br>

Something in it

When I recently modified a project, I encountered this problem and found another convenient solution:
It is to change the names of all namespaces as long as they are different from the original ones.
Because I want to create a new project, I need to update a namespace.