Silverlight compile error - The tag 'Label' does not exist in XML namespace

I was working on a silverlight form in an application. I was trying to add some validations and other related controls on the page. So I had added Label control on the page. I declared the xml namespace and associated tags at the top of the control file as well. When I tried to compile the application, I got the following error. I looked at the declarations, my SDK folder to make sure that I have the required SDK assemblies, I looked in GAC etc. Everything looked good and I still could not figure out what the problem is.

What is the problem?

After spending good bit of time, I decided to look at one of the sample in SDK. I still could not figure out the issue. Then I decided to copy and paste the xml namespace and tags from the sample to my XAML file. Now everything worked fine. When I closely looked at the declaration, I saw the issue. See below, the one in red is wrong and one in green is good.

xmlns:dataInput="clr-namespace:System.Windows.Controls;assembly= System.Windows.Controls.Data.Input"

xmlns:dataInput="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.Input"

You can see I had an extra white space after assembly=. It seems that compiler is literally parsing the string and trying to look for assembly file with name as is in the statement. Instead of giving error message that some namespace or control does not exist in the assembly, the correct error message should have been that assembly with name or path could not be found. I could not complain much either because I am using Visual Studio 2010 Beta and beta version has lot of room for improvement.