Error 6 The tag 'CrystalReportsViewer' does not exist in XML namespace 'clr

有时候你会遇到这样的问题

Error6Thetag'CrystalReportsViewer'does notexistinXMLnamespace
'clr-
namespace:SAPBusinessObjects.WPF.Viewer;assembly=SAPBusinessObjects.WPF.Viewer'. 
Line6Position10

在网上搜了一下，其解决方法为：

To resolve this error you need to go to the properties of the project and set the Target Framework to .NET Framework 4 not the .NET Framework 4 Client Profile. I'm not sure if this is a bug in the Beta version so hopefully you won't have to do this when the production copy is released.

就是将“项目”中“属性”框中的.NET Framework 4 Client Profile改为.NET Framework 4。

原文来自：http://aspalliance.com/1991_Using_the_New_WPF_Viewer_with_SAP_Crystal_Reports_for_Visual_Studio_2010.2