C#.net object reference error

Question

How you tell me how to change the C#.net desktop 2008 logic so it will compile clean and the logic works? The problem is I am trying to create an instance of an object in a static class

In this application I want to create a 'class with methods for accessing the active directory' from all parts of the solution file. As part of this logic change when a user clicks on the desktop shortcut and they are not assigned to any active directory groups, I want to throw an error message stating 'do not have access-contact network administrator and throw them out of the application.

The logic to check the user credentials comes from the main method that is a 'static' method in program.cs.

The code I want to add to the main methos is as follows:

ActiveDirectoryUser CurUser;

CurUser = new ActiveDirectoryUser();

However I get the following errors:

-
Error 55 'Desktop.CurUser': cannot declare instance members in a static class

Error 56 The type or namespace name 'ActiveDirectoryUser' could not be found (are you missing a using directive or an assembly reference?)

Error 57 The type or namespace name 'ActiveDirectoryUser' could not be found (are you missing a using directive or an assembly reference?)

The cLass i want to reference looks like the following:

using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Reflection;
using System.IO;
using System.Threading;
using System.Web;
using System.Windows.Forms;
using System.Security.Principal;

namespace EnrollTrac.Common
{
public class ActiveDirectoryUser
{
public ActiveDirectoryUser()
{
AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal);
Thread.CurrentPrincipal = new WindowsPrincipal(WindowsIdentity.GetCurrent());

if ((!Thread.CurrentPrincipal.IsInRole("testit")))


{
MessageBox.Show("You do not have authortity.Please contact your network administrator"," Error", essageBoxButtons.OK, MessageBoxIcon.Error);
return;

}

else

{
Application.Run(new Desk());
break;
}