For using tab control in silverlight, we have to drag and drop into panel and configure the control like this
<Grid x:Name="LayoutRoot" Background="White">
<sdk:TabControl Height="300" HorizontalAlignment="Left" Margin="10,10,0,0" Name="tabControl1" VerticalAlignment="Top" Width="500">
<sdk:TabItem Header="Asp.net">
<StackPanel Background="BlueViolet"><TextBlock Text="This is the asp.net tab"/>
</StackPanel>
</sdk:TabItem><sdk:TabItem Header="Silverlight">
<StackPanel Background="Brown"><TextBlock Text="This is the Silverlight"/>
</StackPanel>
</sdk:TabItem>
<sdk:TabItem Header="Asp.net MVC">
<StackPanel Background="Coral"><TextBlock Text="This is the Asp.net MVC"/>
</StackPanel>
</sdk:TabItem></sdk:TabControl>
</Grid>