Validating in WPF

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Hi,

How do I ask the validation in this form of code created by Blend?

<TextBox Margin="2,2,2,2 " ToolTip="Client s address" Text="{Binding
Path=CurrentRow .ClientAddress, Mode=Default}" TextWrapping="W rap"
Grid.Column="1" Grid.Row="2" d:LayoutOverrid es="Height"/>

In the examples I fould the code is like this:

<TextBox Margin="5" Grid.Column="1" >
<TextBox.Text >
<Binding Path="ModelNumb er">
<Binding.Valida tionRules>
<DataErrorValid ationRule></DataErrorValida tionRule>
</Binding.Validat ionRules>
</Binding>
</TextBox.Text>
</TextBox>

Thanks,
Marco Castro