How to: Set ToolTips for Controls on a Windows Form at Design Time
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To set a ToolTip programmatically
To set a ToolTip in the designer
Add a ToolTip component to the form.
Select the control that will display the ToolTip, or add it to the form.
In the Properties window, set the ToolTip on ToolTip1 value to an appropriate string of text.