判断设计时

public static bool IsInDesignMode()
        {
            bool returnFlag = false;
#if DEBUG
            if (System.ComponentModel.LicenseManager.UsageMode == System.ComponentModel.LicenseUsageMode.Designtime)
            {
                returnFlag = true;
            }
            else if (System.Diagnostics.Process.GetCurrentProcess().ProcessName.ToUpper().Equals("DEVENV"))
            {
                returnFlag = true;
            }
#endif
            return returnFlag;
        }