Why two columns in a WPF Grid with * do not have the same size?

Question

with the following code I expected to end with two ListBox with the same Width as they are into two columndefinition with With="*"

Instead of this looks like the size is determined from the size of the text up the ListBox which does not make sense as this text is much smaller than the ListBox and thus the TextBlock has enough space to accommodate the text.

<Window x:Class="UnderstandSizing.Window5"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window5" 
SizeToContent="WidthAndHeight"
ResizeMode="NoResize" >

<Grid>  
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>

    <TextBlock Text="Text1longer" Grid.Row="0" Grid.Column="0" x:Name="Test1" />
    <TextBlock Text="Text1" Grid.Row="0" Grid.Column="2" />
    <ListBox Grid.Row="1" Grid.Column="0" Height="150" />

    <ListBox Grid.Row="1" Grid.Column="2" Height="150" />
    <TextBlock Grid.Row="2" Grid.ColumnSpan="3"  Text="This textblock sets the max width" Width="300" />
</Grid>
</Window>

The WPF automatic sizing feature is driving me mad ... any ideas? Thanks.

EDIT: Everything done in VS2008, just in case it matters.

Styria

Answer 1

Alex. A found the exact cause of what is happening and I found a solution in a lucky strike. Just changing the * for 0 I get the expected result (weird if you ask me):

<Window x:Class="UnderstandSizing.Window5"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window5" 
SizeToContent="WidthAndHeight"
ResizeMode="NoResize" >

<Grid>  
<Grid.ColumnDefinitions>
    <ColumnDefinition Width="0" />
    <ColumnDefinition Width="Auto" />
    <ColumnDefinition Width="0" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
    <RowDefinition Height="Auto" />
    <RowDefinition Height="Auto" />
    <RowDefinition Height="Auto" />
</Grid.RowDefinitions>

<TextBlock Text="Text1longer" Grid.Row="0" Grid.Column="0" x:Name="Test1" />
<TextBlock Text="Text1" Grid.Row="0" Grid.Column="2" />
<ListBox Grid.Row="1" Grid.Column="0" Height="150" />

<ListBox Grid.Row="1" Grid.Column="2" Height="150" />
<TextBlock Grid.Row="2" Grid.ColumnSpan="3"  Text="This textblock sets the max width" Width="300" />
</Grid>
</Window>

Styria

Answer 2

Look at this:

http://www.wpftutorial.net/GridLayout.html

"Star (*):

Takes as much space as available (after filling all auto and fixed sized columns), proportionally divided over all star-sized columns. So 3*/5* means the same as 30*/50*. Remember that star-sizing does not work if the grid size is calculated based on its content."

Which is the case in your code. I suspect this also is the reason it looked alright for others testing it, if they pasted the Grid into a Window larger than the 300 pixels set by your TextBlock. I get the same issue you do if I use exactly the same XAML.

Edit: So that's for the "why". See this question for a possible alternative solution: Wpf: Grid: How can i share column/row height width?

The most recent answer (not the one chosen by asker) seems to be the most useful one in this case.

Incurvate

I had exactly the same code in a window on it's own and couldn't reproduce. Using VS2010 and .NET 4.0 though. – Bechuanaland

Odd. I'm using the same, and it was reproduced, except that the column widths were denoted as 1* as expected. But actual widths were 167 and 133. – Incurvate

I've found a really odd solution. If I change the * for 0 I get the desired functionality :\ – Styria

Interesting, though I'd recommend not using it. It might work now, but who knows what could happen later on, unless this behaviour is specified somewhere. – Incurvate

Going about it the proper way might save you sweat later on. – Incurvate

Answer 3

For me this works just fine, at runtime that is. Do not trust GUI designers, they are the enemy.

Nudibranch

Answer 4

Works for me at design time and at runtime.

The GUI designer shouldn't be showing those pixel sizes. For me it shows 1*, which means your screenshot is from code different than you pasted.

Bechuanaland

Not at all. From IDE to SO, directly, no changes done. Working with VS2008. Maybe this matters. – Styria

@SoMoS weird. I was using exactly the same code. Nothing else in the window or even in the project. .NET version? I was using 4.0 and VS2010 – Bechuanaland

Sure it is. I'm using NET 3.5 and VS2008 – Styria