yourToolTip = new ToolTip();
//The below are optional, of course,
yourToolTip.ToolTipIcon = ToolTipIcon.Info;
yourToolTip.IsBalloon = true;
yourToolTip.ShowAlways = true;
yourToolTip.SetToolTip(lblYourLabel,"Oooh, you put your mouse over me.");原文：https://www.cnblogs.com/zeroone/p/9689749.html