System.Environment.Environment.GetEnvironmentVariable C# (CSharp) Method

		public static string GetEnvironmentVariable (string variable, EnvironmentVariableTarget target)
		{
			switch (target) {
			case EnvironmentVariableTarget.Process:
				return GetEnvironmentVariable (variable);
			case EnvironmentVariableTarget.Machine:
				new EnvironmentPermission (PermissionState.Unrestricted).Demand ();
				if (!IsRunningOnWindows)
					return null;
				using (Microsoft.Win32.RegistryKey env = Microsoft.Win32.Registry.LocalMachine.OpenSubKey (@"SYSTEM\CurrentControlSet\Control\Session Manager\Environment")) {
					object regvalue = env.GetValue (variable);
					return (regvalue == null) ? null : regvalue.ToString ();
				}
			case EnvironmentVariableTarget.User:
				new EnvironmentPermission (PermissionState.Unrestricted).Demand ();
				if (!IsRunningOnWindows)
					return null;
				using (Microsoft.Win32.RegistryKey env = Microsoft.Win32.Registry.CurrentUser.OpenSubKey ("Environment", false)) {
					object regvalue = env.GetValue (variable);
					return (regvalue == null) ? null : regvalue.ToString ();
				}
			default:
				throw new ArgumentException ("target");
			}
		}