Yes, delete will work. Means, use this code to toggle:
public void ToggleTaskManager()
{
RegistryKey objRegistryKey = Registry.CurrentUser.CreateSubKey(
@"Software\Microsoft\Windows\CurrentVersion\Policies\System");
if (objRegistryKey.GetValue("DisableTaskMgr") == null)
objRegistryKey.SetValue("DisableTaskMgr", "1");
else
objRegistryKey.DeleteValue("DisableTaskMgr");
objRegistryKey.Close();
}
or this code to set:
public void SetTaskManager(bool enable)
{
RegistryKey objRegistryKey = Registry.CurrentUser.CreateSubKey(
@"Software\Microsoft\Windows\CurrentVersion\Policies\System");
if (enable && objRegistryKey.GetValue("DisableTaskMgr") != null)
objRegistryKey.DeleteValue("DisableTaskMgr");
else
objRegistryKey.SetValue("DisableTaskMgr", "1");
objRegistryKey.Close();
}