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

		public static void SetEnvironmentVariable (string variable, string value, EnvironmentVariableTarget target)
		{
			if (variable == null)
				throw new ArgumentNullException ("variable");
			if (variable == String.Empty)
				throw new ArgumentException ("String cannot be of zero length.", "variable");
			if (variable.IndexOf ('=') != -1)
				throw new ArgumentException ("Environment variable name cannot contain an equal character.", "variable");
			if (variable[0] == '\0')
				throw new ArgumentException ("The first char in the string is the null character.", "variable");

			switch (target) {
			case EnvironmentVariableTarget.Process:
				InternalSetEnvironmentVariable (variable, value);
				break;
			case EnvironmentVariableTarget.Machine:
				if (!IsRunningOnWindows)
					return;
				using (Microsoft.Win32.RegistryKey env = Microsoft.Win32.Registry.LocalMachine.OpenSubKey (@"SYSTEM\CurrentControlSet\Control\Session Manager\Environment", true)) {
					if (String.IsNullOrEmpty (value))
						env.DeleteValue (variable, false);
					else
						env.SetValue (variable, value);
					internalBroadcastSettingChange ();
				}
				break;
			case EnvironmentVariableTarget.User:
				if (!IsRunningOnWindows)
					return;
				using (Microsoft.Win32.RegistryKey env = Microsoft.Win32.Registry.CurrentUser.OpenSubKey ("Environment", true)) {
					if (String.IsNullOrEmpty (value))
						env.DeleteValue (variable, false);
					else
						env.SetValue (variable, value);
					internalBroadcastSettingChange ();
				}
				break;
			default:
				throw new ArgumentException ("target");
			}
		}