Element <element> is not a known element warning in Visual Studio when using User controls

asp.net visual-studio webforms user-controls warnings
chris picture chris · Jan 29, 2009 · Viewed 68.3k times · Source

I have a Visual Studio 2008 project that is showing the following warning when using User Controls, and I haven’t been able to find a solution anywhere.

Element <element>is not a known element

How can I fix this?

Answer

Jason Snelders picture Jason Snelders · Sep 25, 2009

This sounds like a classic re-build your solution and "close and re-open Visual Studio" problem.

It's possible it may also be related to a similar problem I had which I answered at Resolving "Validation (): Element ‘xxxx’ is not supported" warning in Visual Studio 2005/2008.

Related questions

WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for 'jquery'. Please add a ScriptResourceMapping named jquery(case-sensitive)

I'm building a web application using Visual Studio 2012. I'm attempting to add word count into my textbox. However after adding the the javascript codes and the html codes. I receive the error as stated above. Here is my javascript codeds …

Read More
How do you force Visual Studio to regenerate the .designer files for aspx/ascx files?

Sometimes when I'm editing page or control the .designer files stop being updated with the new controls I'm putting on the page. I'm not sure what's causing this to happen, but I'm wondering if there's any way of forcing Visual …

Read More
ASP.NET Web Site or ASP.NET Web Application?

When I start a new ASP.NET project in Visual Studio, I can create an ASP.NET Web Application or I can create an ASP.NET Web Site. What is the difference between ASP.NET Web Application and ASP.NET …

Read More