Programming WPF, 2nd Edition

ToolTip

The ToolTip control allows a floating label to be displayed above some part of the user interface. It is an unusual control in that it cannot be part of the normal user interface tree—you can use it only in conjunction with another element. It becomes visible only when the mouse pointer hovers over the target element, as Figure 5-14 shows.

Figure 5-14. TextBox with ToolTip

To associate a ToolTip with its target element, you set it as the ToolTip property of its target, as shown in Example 5-11.

Example 5-11. Using ToolTip the long way

<TextBox Width="100">
  <TextBox.ToolTip>
    <ToolTip Content="Type something here" />
  </TextBox.ToolTip>
</TextBox>

In fact, you don't need to specify the ToolTip object explicitly. You can just set the ToolTip property to a string, as shown in Example 5-12.

Example 5-12. Using ToolTip the short way

<TextBox Width="100" ToolTip="Type something here" />

If you set the property to anything other than a ToolTip, WPF creates the ToolTip control for you, and sets its Content property to the value of the target element's ToolTip property. Example 5-11 and Example 5-12 are therefore equivalent.

ToolTip derives from ContentControl, so its content is not restricted to simple strings—we can put anything we like in there, as shown in Example 5-13.

Example 5-13. Exploiting the content model in a tool tip

<TextBox Width="100"> <TextBox.ToolTip> <TextBlock FontSize="25"> ...