Why Width="*" doesn't work for columns in DataGrid located in RowDetailsTemplate

Question

If I set widths of DataGrid (located in RowDetailesTemplate) columns using "*" - columns scaling doesn't work

<DataGrid>
...
<DataGrid.RowDetailsTemplate>
   <DataTemplate>
      <DataGrid Margin="10" Height="100">
         <DataGrid.Columns>
            <DataGridTextColumn Header="header A" Width="3*" />
            <DataGridTextColumn Header="header B" Width="2*" />
            <DataGridTextColumn Header="header C" Width="*" />
         </DataGrid.Columns>
      </DataGrid>
    </DataTemplate>
</DataGrid.RowDetailsTemplate>
</DataGrid>

but if I replace DataGrid by Grid and set it's columns width using "*" scailing works

<Grid Margin="5" Height="100">
   <Grid.ColumnDefinitions>
      <ColumnDefinition Width="3*"></ColumnDefinition>
      <ColumnDefinition Width="2*"></ColumnDefinition>
      <ColumnDefinition Width="*"></ColumnDefinition>
   </Grid.ColumnDefinitions>

   <TextBlock Text="header A" Background="LightGray" TextAlignment="Center" HorizontalAlignment="Stretch"></TextBlock>
   <TextBlock Text="header B" Grid.Column="1" TextAlignment="Center" HorizontalAlignment="Stretch"></TextBlock>
   <TextBlock Text="header C" Grid.Column="2" Background="LightGray" TextAlignment="Center" HorizontalAlignment="Stretch"></TextBlock>
</Grid>

how to fix DataGrid scaling ?

solution:

<DataGrid HorizontalScrollBarVisibility="Disabled">
...
<DataGrid.RowDetailsTemplate>
...
</DataGrid.RowDetailsTemplate>
</DataGrid>

Answer 1

It is just a guess based on this question.

Set ScrollViewer.HorizontalScrollBarVisibility="Disabled".