Hi,
I ran across the same problem as I added ultrawebgrid in the project (Infragistics2.WebUI.UltraWebGrid.v9.1.dll), and tried to fix it by the following article as suggested:
http://help.infragistics.com/Help/NetAdvantage/NET/2008.3/CLR2.0/html/Web_Adding_an_Assembly_to_a_Project.html
But it did not worked for me. All I had to do was to add the dll (Infragistics2.WebUI.Shared.v9.1.dll) in the project, and the build was successful.
In the same way you'd manually add a reference to any other assembly. The following article from our online help files for NetAdvantage for .NET 2008 Volume 3 provide additional information, including links to relevant MSDN articles:Adding an Assembly to a Project
i got the same errors while using Ultrawebmenu and all other infragistic components
how can I add the missing reference to the Infragistics2.WebUI.Shared.v8.3 assembly??
It looks like your website is missing a reference to the Infragistics2.WebUI.Shared.v8.3 assembly, or that it's expecting a version of this assembly (8.3.20083.1009) that's different than the one you have. Add a reference to this version of this assembly to your project.
In general, this reference should be added automatically. You might also want to consider re-running the Toolbox Utility to ensure that your Visual Studio Toolbox tabs refer the same version of the NetAdvantage assemblies that you have installed.