WPF产生不重复的随机数

<Grid>
        <TextBlock x:Name="tb_Screen" HorizontalAlignment="Left" Margin="59,24,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top"/>
        <Button x:Name="tb_Create" Content="Button" HorizontalAlignment="Left" Margin="144,259,0,0" VerticalAlignment="Top" Width="75" Click="tb_Create_Click"/>
        <TextBox x:Name="txt_min" HorizontalAlignment="Left" Height="23" Margin="80,92,0,0" TextWrapping="Wrap" Text="50" VerticalAlignment="Top" Width="70" RenderTransformOrigin="0.462,2.179"/>
        <TextBox x:Name="txt_max" HorizontalAlignment="Left" Height="23" Margin="257,92,0,0" TextWrapping="Wrap" Text="99" VerticalAlignment="Top" Width="82" RenderTransformOrigin="1.018,0.43"/>
        <TextBlock HorizontalAlignment="Left" Margin="10,95,0,0" TextWrapping="Wrap" Text="min=" VerticalAlignment="Top"/>
        <TextBlock HorizontalAlignment="Left" Margin="186,95,0,0" TextWrapping="Wrap" Text="max=" VerticalAlignment="Top"/>
        <TextBox x:Name="txt_n" HorizontalAlignment="Left" Height="23" Margin="121,149,0,0" TextWrapping="Wrap" Text="10" VerticalAlignment="Top" Width="120"/>
        <TextBlock HorizontalAlignment="Left" Margin="31,152,0,0" TextWrapping="Wrap" Text="数量" VerticalAlignment="Top"/>
</Grid>