ASP.NET、WinForm - 判断整个页面文本框是否为空

foreach(Control ctrl in Page.Controls)
	{
		foreach(Control childc in ctrl.Controls)
		{
			switch(childc.GetType().ToString())
			{
				case "System.Web.UI.WebControls.TextBox" :
					TextBox txt = (TextBox)childc;
					txt.ReadOnly = true;
					break;
				case "System.Web.UI.WebControls.Label" :
					Label lbl = (Label) childc;					
					break;
				case "System.Web.UI.WebControls.DropDownList" :
					DropDownList ddl = (DropDownList) childc;					
					break;
			}
		}
	}