Using ToolTip for TextBox with TextBox.ToolTip and ToolTip tag
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" HorizontalAlignment="Center" VerticalAlignment="Center"> <TextBox Width="100"> <TextBox.ToolTip> <ToolTip Content="Type something here" /> </TextBox.ToolTip> </TextBox> </Page>