using System;
using System.Collections;
using System.Security.Permissions;

public class Starter
{
	public static void Main()
	{
		IDictionary environ=Environment.GetEnvironmentVariables();
		ICollection keys=environ.Keys;	
		System.Object [] values=new System.Object[environ.Count];
		keys.CopyTo(values, 0);
		foreach(string s in values)
			Console.WriteLine(s);
		
		string environvars="USERNAME;OS";
		EnvironmentPermission ep=new EnvironmentPermission(
			EnvironmentPermissionAccess.AllAccess,
			environvars);
		ep.Deny();
		GetUser();
	}

	public static void GetUser()
	{
		string user=Environment.UserName;	
	}
}