Within my project I have gotten this error:
Error 1 The type or namespace name 'UI' does not exist in the namespace 'System.Web' (are you missing an assembly reference?)
So, basically I attempted to add "system.web" as a reference to my project, but there is no such thing exist in my .NET framework.
How can I install "system.web"?
If the kind of project the reference is being added to is not a web project, then you may need to right click the project and change the target framework from .NET 4 Client to just .NET 4.
In your solution/project, expand the node 'References' & see if there is an icon indicating System.Web is missing. If yes, then right click and add reference.
In the add reference window, click on .NET tab and scroll down to System.Web reference and click on OK.
System.Web is installed as part of .NET Framework. Make sure you have .net framework installed on your machine, if not install it from windows update or from microsoft.com and later open your project to make sure the assembly is referenced.
Hope it helps.