windows - How to open a new web page by clicking a button - visual studio 12, C# and XAML app

Question

I'm trying to create a button that will open a new web page by clicking it. I have found that something like the following code would work but Visual Studio 12 doesn't recognize the namespace Process.

C#

{ 
    private void button_Click_1(object sender, RoutedEventArgs e)
    {
        System.Diagnostics.Process.Start("http://www.stackoverflow.com");
    }
}

XAML

<Button Content="button" x:Name="clock" Click="button_Click_1" IsEnabled="{Binding Source=button}"/>

Any ideas? Thank you!