Theming
Telerik themes are not turned on by default in RadToolTip. In order to use the predefined Telerik styles you can define a ContentTemplate for the RadToolTip component and use the RadToolTipContentView control inside the template.
The following code example demonstrates how to set up RadToolTip to use the Telerik themes.
Example 1: Setting ToolTipContentTemplate property
<Ellipse Width="80" Height="80" Fill="#FF1B9DDE" Stroke="#FF1B9DDE" StrokeThickness="2"
telerik:RadToolTipService.Placement="Top"
telerik:RadToolTipService.VerticalOffset="-10"
telerik:RadToolTipService.ToolTipContent="RadToolTip">
<telerik:RadToolTipService.ToolTipContentTemplate>
<DataTemplate>
<telerik:RadToolTipContentView>
<TextBlock Text="{Binding}" />
</telerik:RadToolTipContentView>
</DataTemplate>
</telerik:RadToolTipService.ToolTipContentTemplate>
</Ellipse>
Example 2: Setting ToolTipContent property
<Ellipse Width="80" Height="80" Fill="#FF1B9DDE" Stroke="#FF1B9DDE" StrokeThickness="2"
telerik:RadToolTipService.Placement="Top"
telerik:RadToolTipService.VerticalOffset="-10"
telerik:RadToolTipService.ToolTipContentTemplate="{x:Null}">
<telerik:RadToolTipService.ToolTipContent>
<telerik:RadToolTipContentView>
<TextBlock Text="RadToolTip" />
</telerik:RadToolTipContentView>
</telerik:RadToolTipService.ToolTipContent>
</Ellipse>
The end result is demonstrated in the picture below: