Row Space Hide(Block)

Question

How to hide(block) the row(s) space through code behind class.

e.g
My application has three rows , each rows contains the panels.
i want to display First & Third row , second row space should be hidden (same like a display: block in WebApp).

My Code:
<Grid.ColumnDefinitions>
            <ColumnDefinition Width="48.75*" />
            <ColumnDefinition Width="241.25*" />
            <ColumnDefinition Width="160*" />           
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25*"  />
            <RowDefinition Height="25*"  />
            <RowDefinition Height="25*"  />           
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
       
<Canvas Grid.Column="1" Grid.Row="5" Grid.RowSpan="4" Margin="0.833,0,1.666,24.99" Name="panel1" Grid.ColumnSpan="4" Background="AliceBlue" Visibility="Hidden"></Canvas>

<Canvas Background="AliceBlue" Grid.ColumnSpan="4" Grid.RowSpan="3" Margin="0.833,1.666,1.666,0" Name="panel2" Grid.Row="8" Grid.Column="1" Visibility="Hidden"></Canvas>

<Canvas Background="AliceBlue" Grid.ColumnSpan="4" Grid.RowSpan="3" Margin="0.833,1.666,1.666,0" Name="panel3" Grid.Row="8" Grid.Column="1" Visibility="Hidden"></Canvas>

Thanks 'n Advance :)