I wanted to use Ajax control toolkit in Sharepoint, and had not had any luck until I spent the whole day debugging and getting it to work. I already had Ajax integrated in Sharepoint, so it should be fairly easy to just add in AjaxControlToolkit, but the problem is the latest version of it actually requires you to use ToolkitScriptManager instead of ScriptManager, otherwise your control will not work and you will see a Javascript error of "Please wait while scripts are loaded".
I had to create a task dynamically in C# and assign the task to a reviewer, which is a user account. However, there was this problem of the "Assigned to" field is only read only. To do that, just create an SPFieldUserValueCollection and assign it to task item.
I needed to get SPUser object from doing a lookup using CAML query, so that I could get the user information such as email address, etc. To do that, this is the code that I used:
I had the problem of not able to debug Sharepoint in Visual Studio 2008 awhile ago, and glad that Aaron shown me how to do it by doing some tricks. What happened was the PDB file might not have been deployed to the assembly GAC.