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

Question

What would be the best/right way to have a set of DataGrid columns have proportional width (Width=\"\\*\"), but to have their minimum

Answer 1

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:

   
      
      
   
   ...

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
{
   /// 

   /// 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.
   /// 
   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);
         }
      }
   }
}