URLEncode Problem with .NET 4.0

Visual Studio 2010 Problem with "The name HttpUtility does not exist in the current context".

I usually use Visual Studio 2010 at work and the Express edition at home. Tonight I was knocking up quick C# windows form application to crawl some specific URL's and I required the ability to URL Encode my URI Components e.g

string url = "http//somesite.com/search?qry=" +  System.Web.HttpUtility.UrlEncode(val);

However even though I had included:

using System.Web;

At the top of my class it was saying that HttpUtility could not be found in System.Web.

This was driving me crazy as I had another project open at the same time which was using the exact same code and it worked.

The advice I found on the web said to ensure that a reference to System.Web was added with the "Project" > "Add References" option.

However when I was searching for this DLL all I could find were System.WebServices and System.ApplicationServices which were obviously no good.

However after a lot of head scratching I went back to the main Project Properties panel and under Target Framework I had ".NET Framework 4 Client Profile" Selected.

I changed this first to .NET Framework 3.5 and then looked again for the reference and it worked!

I added it and then changed it back again to .NET Framework 4. On re-opening the project  all my problems had been solved.

Don't ask me why System.Web doesn't appear as a reference under the Client versions but it doesn't and you need to add a proper DLL reference to get to use this sort of functionality if you are doing non web based apps that require web based functionality like URL or HTML Encode etc.

I thought I would just write a few notes about this in-case anyone else experiences the same problem.