What does the WPF star do (Width="100*")

Shimmy_75500 0
Viewed 99294

What does exactly the star in size terms in WPF mean?

grid size xaml wpf
4 Answers

In a WPF Grid, Width="*" or Height="*" means proportional sizing.
For example: to give 30% to column 1 and 70% to column 2 -

<ColumnDefinition Width="3*" />
<ColumnDefinition Width="7*" />

enter image description here

And likewise for rows -

<RowDefinition Height="3*" />
<RowDefinition Height="7*" />

The numbers do not have to be integers.
If the Width for RowDefinition (Height for ColumnDefinition) is omitted, 1* is implied.
In this example, column 1 is 1.5 times wider than column 2 -

<ColumnDefinition Width="1.5*" />
<ColumnDefinition />

Column 1: 1.5*, Column 2 1* (implied)

You can mix auto-fit and fixed widths with * (proportional) widths; in that case the * columns are apportioned to the remainder after the auto-fit and fixed widths have been calculated - 

<Grid.ColumnDefinitions>
    <ColumnDefinition Width="Auto" />  <!-- Auto-fit to content, 'Hi' -->
    <ColumnDefinition Width="50.5" />  <!-- Fixed width: 50.5 device units) -->
    <ColumnDefinition Width="69*" />   <!-- Take 69% of remainder -->
    <ColumnDefinition Width="31*"/>    <!-- Take 31% of remainder -->
</Grid.ColumnDefinitions>
<TextBlock Text="Hi" Grid.Column="0" />

enter image description here

user_1586750

we take following example.....

A grid has 3 columns each containing one button of width 100.

enter image description here

XAML Code is...

    <Grid x:Name="LayoutRoot" Width="600">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="3*" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="10,10,0,0" Name="button1" VerticalAlignment="Top" Width="100" />
    <Button Content="Button1" Height="23" HorizontalAlignment="Left" Margin="0,10,0,0" Name="button2" VerticalAlignment="Top" Width="100" Grid.Column="1" />
    <Button Content="Button2" Height="23" HorizontalAlignment="Left" Margin="0,10,0,0" Name="button3" VerticalAlignment="Top" Width="100" Grid.Column="2" />
</Grid>

But actually its size is....

<Grid.ColumnDefinitions>
        <ColumnDefinition Width="375" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="125" />
</Grid.ColumnDefinitions>

Conclusions:

  • Total size of grid is 600

  • Auto : Column is resizes based on it's contents. (2nd column has button of width 100)

  • * : 1st column width is 3x of 3rd column.

user_6728910
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