How can limit the height of a grid row in wpf - wpf

Question

I'm developing an Outlook Add-in in WPF. Outlook Add-in is an UserControl. My simplified XAML code look's :
<UserControl>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="150"/>
<RowDefinition Height="*"/>
<RowDefinition Height="20"/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0">Header</TextBlock>
<ListBox Grid.Row="1"></ListBox>
<Button Grid.Row="2"></Button>
</Grid>
</UserControl>
The list box items are loaded dynamically. With the help of this class that I founded here http://www.codeproject.com/KB/WPF/GridLengthAnimation.aspx the height of the 3rd row is set to 0.4* when the button is pressed.
The problem is that when I have more items in the list box the second row expands and the 3rd row disappears.The solution could be if I set the MaxHeight of the second row to 100% height-170, but I don't know the available height for the UserControl.
Any ideas?

Answer 1

Instead of specifying Height try specifying MinHeight for the 3rd row, that way it won't shrink beyond a certain size.

Answer 2

The problem was here ( on the library that I've used )
public override object GetCurrentValue(object defaultOriginValue,
object defaultDestinationValue, AnimationClock animationClock)
{
double fromVal = ((GridLength)GetValue(GridLengthAnimation.FromProperty)).Value;
double toVal = ((GridLength)GetValue(GridLengthAnimation.ToProperty)).Value;
if (fromVal > toVal)
{
return new GridLength((1 - animationClock.CurrentProgress.Value) * (fromVal - toVal) + toVal, GridUnitType.Pixel);
}
else
return new GridLength(animationClock.CurrentProgress.Value * (toVal - fromVal) + fromVal, GridUnitType.Pixel);
}
I've replaced GridUnitType.Star with GridUnitType.Pixel. And now it work's perfectly