Add pop up message box in c#

ClientScript.RegisterStartupScript(GetType(), "Message", "");

Request.PathInfo

Request.PathInfo is a little known property that returns the path information for a resource with a URL extension

User doesnot hace permission to do this action

When you receieve this error as "User doesnot hace permission to do this action" This is maily because the application run under a process which doen't have sufficient permissions to perform action. In case of Visual Studio if you receieve tis error then it means that the ASPNET doesn't have permissions to perform this action. to overcome this errror you should do the following:
1) Give permission for the ASPNET to perform this action
2) or make your application run under another account than ASPNET.

Read about (1) and let me know too.

But for the second option use the impersonate setting account in the web config file that would resolve this issue. This would tell the ASPNET that use specified crenditials to update information.
identity impersonate="true" userName="xx" password="xx"/

I would also recommend following article with it.
http://support.microsoft.com/default.aspx?scid=kb;en-us;329290