2005下使用:
        /// <summary>
        /// 查找是否已创建窗体
        /// </summary>
        /// <param name="FormName">窗体Name</param>
        /// <returns></returns>
        public static bool SearchAllForm(string FormName)
        {
            for (int i = 0; i < Application.OpenForms.Count; i++)
            {
                if (Application.OpenForms[i].Name == FormName)
                {
                    return true;
                }
            }
            return false;
        }
2003下使用:        [DllImport("User32.dll", EntryPoint = "FindWindow")]
        private static extern IntPtr FindWindow(string lpClassName, string lpWindowName);        [DllImport("user32.dll", EntryPoint = "FindWindowEx")] //找子窗体
        private static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);        [DllImport("User32.dll", EntryPoint = "SendMessage")] //用于发送信息给窗体
        private static extern int SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, string lParam);
        /// <summary>
        /// 查找是否已创建窗体
        /// </summary>
        /// <param name="FormTitle">标题名称</param>
        /// <returns></returns>
        public static bool SearchForm(string FormTitle)
        {
            IntPtr ParenthWnd = new IntPtr(0);
            IntPtr EdithWnd = new IntPtr(0);            //查到窗体,得到整个窗体 
            ParenthWnd = FindWindow(null,FormTitle);
            if (!ParenthWnd.Equals(IntPtr.Zero))
            {
                return true;
            }
            else
            {
                return false;
            }        }