Set font size and font family for TextBlock
<UserControl x:Class='SilverlightApplication3.MainPage' xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml' xmlns:d='http://schemas.microsoft.com/expression/blend/2008' xmlns:mc='http://schemas.openxmlformats.org/markup-compatibility/2006' mc:Ignorable='d' d:DesignWidth='640' d:DesignHeight='480'> <Canvas x:Name="LayoutRoot" Background="White"> <TextBlock x:Name="headingText" Text="Please Login" Canvas.Top="10" Canvas.Left="10" FontFamily="Times New Roman" FontSize="18" /> </Canvas> </UserControl>