WPF - DataGrid Column with Width="*", but MinWidth to Fit Contents

user_260156 0
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What would be the best/right way to have a set of DataGrid columns have proportional width (Width="\*"), but to have their minimum width be at least the width of their content? At the moment, if I use Width="*", then the columns stay exactly proportional, but content gets cropped if the columns get too thin. If I use Width="Auto", then the columns size themselves perfectly to their content, but this makes them all different sizes.

What I want is really a combination of the two, like Width="\*", MinWidth="Auto" so that when there's extra width the columns will all space out to equal widths, but when the grid is made smaller, the content never gets cropped.

Sadly, MinWidth="Auto" doesn't exist, so I guess I need to bind the column's MinWidth property, but it's hard to figure out exactly what I would bind it to.

How do I tell WPF "MinWidth=" the width of the column's widest piece of content?

datagridcolumn datagrid width xaml wpf
5 Answers

You can create a dependency property (called e.g. HorizontalPropFillOfBlankSpace) for Grid control which will ensure what you need (columns with Width="*", but MinWidth to fit contents). Then you can apply it on any grid you want:

<Grid namespace:GridHelper.HorizontalPropFillOfBlankSpace="True">
   <Grid.ColumnDefinitions>
      <ColumnDefinition Width="Auto" />
      <ColumnDefinition Width="Auto" />
   </Grid.ColumnDefinitions>
   ...

You can see an example of the implementation of this dependency property below. Only columns with Width="Auto" are automatically resized to fill gap space. It can be customized by you what you need.

public class GridHelper
{
   /// <summary>
   /// Columns are resized to proportionally fill horizontal blank space.
   /// It is applied only on columns with the Width property set to "Auto".
   /// Minimum width of columns is defined by their content.
   /// </summary>
   public static readonly DependencyProperty HorizontalPropFillOfBlankSpaceProperty =
      DependencyProperty.RegisterAttached("HorizontalPropFillOfBlankSpace", typeof(bool), typeof(GridHelper), new UIPropertyMetadata(false, OnHorizontalPropFillChanged));

   public static bool GetHorizontalPropFillOfBlankSpace(Grid grid)
      => (bool)grid.GetValue(HorizontalPropFillOfBlankSpaceProperty);

   public static void SetHorizontalPropFillOfBlankSpace(Grid grid, bool value)
      => grid.SetValue(HorizontalPropFillOfBlankSpaceProperty, value);

   private static void OnHorizontalPropFillChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   {
      if (!(d is Grid grid))
         return;

      if ((bool)e.NewValue)
      {
         grid.Loaded += Grid_Loaded;
      }
      else
      {
         grid.Loaded -= Grid_Loaded;
      }
   }

   private static void Grid_Loaded(object sender, RoutedEventArgs e)
   {
      if (!(sender is Grid grid))
         return;

      foreach (var cd in grid.ColumnDefinitions)
      {
         if (cd.Width.IsAuto && cd.ActualWidth != 0d)
         {
            if (cd.MinWidth == 0d)
               cd.MinWidth = cd.ActualWidth;
            cd.Width = new GridLength(1d, GridUnitType.Star);
         }
      }
   }
}
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