in order to use the FolderBrowserDialog control in asp.net, i had to add a reference to System.Windows.Forms in my project. i wrote this code: FolderBrowserDialog f = new FolderBrowserDialog(); f.ShowDialog(); but this error occured: Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it. This exception is only raised if a debugger is attached to the process. any help?