"Pro WPF with VB 2008: Windows Presentation Foundation with .NET 3.5"
That??™s because of the way that the ToolTip measures its content. Figure 7-4. Placing a tooltip explicitly Setting ToolTipService Properties There are some tooltip properties that can??™t be configured using the properties of the ToolTip class. In this case, you need to use a different class, which is named ToolTipService. ToolTipService allows you to configure the time delays associated with the display of a tooltip. All the properties of the ToolTipService class are attached properties, so you can set them directly in your control tag, as shown here:
The ToolTipService class defines many of the same properties as ToolTip. This allows you to use a simpler syntax when you??™re dealing with text-only tooltips. Rather than adding a nested ToolTip element, you can set everything you need using attributes:
CHAPTER 7 n CLASSIC CONTROLS 202 Table 7-3 lists the properties of the ToolTipService class. The ToolTipService class also provides two routed events: ToolTipOpening and ToolTipClosing. You can react to these events to fill a tooltip with just-in-time content or to override the way tooltips work. For example, if you set the handled flag in both events, tooltips will no longer be shown or hidden automatically.