Force resize of GridView columns inside ListView

I have a ListView WPF control with a GridView. I'd like to resize the GridView columns when the content of the columns changes.

I have several distinct data sets but when I change fr开发者_Python百科om one to another, the size of each columns fits the previous data. I'd like to update dynamically. How can I do that?

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Finally, some results on this one. I've found a way to do the same auto-sizing that is done initially and when the gripper on a column header is double clicked.

public void AutoSizeColumns()
{
    GridView gv = listView1.View as GridView;
    if (gv != null)
    {
        foreach (var c in gv.Columns)
        {
            // Code below was found in GridViewColumnHeader.OnGripperDoubleClicked() event handler (using Reflector)
            // i.e. it is the same code that is executed when the gripper is double clicked
            if (double.IsNaN(c.Width))
            {
                c.Width = c.ActualWidth;
            }
            c.Width = double.NaN;
        }
    }
}

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Building on top of Oskars answer, here is a blend behavior to automatically size the columns when the content changes.

 /// <summary>
 /// A <see cref="Behavior{T}"/> implementation which will automatically resize the automatic columns of a <see cref="ListView">ListViews</see> <see cref="GridView"/> to the new content.
 /// </summary>
 public class GridViewColumnResizeBehaviour : Behavior<ListView>
 {
      /// <summary>
      /// Listens for when the <see cref="ItemsControl.Items"/> collection changes.
      /// </summary>
      protected override void OnAttached()
      {
          base.OnAttached();

          var listView = AssociatedObject;
          if (listView == null)
              return;

          AddHandler(listView.Items);
      }

      private void AddHandler(INotifyCollectionChanged sourceCollection)
      {
          Contract.Requires(sourceCollection != null);

          sourceCollection.CollectionChanged += OnListViewItemsCollectionChanged;
      }

      private void RemoveHandler(INotifyCollectionChanged sourceCollection)
      {
          Contract.Requires(sourceCollection != null);

          sourceCollection.CollectionChanged -= OnListViewItemsCollectionChanged;
      }

      private void OnListViewItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs notifyCollectionChangedEventArgs)
      {
          var listView = AssociatedObject;
          if (listView == null)
              return;

          var gridView = listView.View as GridView;
          if (gridView == null)
              return;

          // If the column is automatically sized, change the column width to re-apply automatic width
          foreach (var column in gridView.Columns.Where(column => Double.IsNaN(column.Width)))
          {
               Contract.Assume(column != null);
               column.Width = column.ActualWidth;
               column.Width = Double.NaN;
          }
      }

      /// <summary>
      /// Stops listening for when the <see cref="ItemsControl.Items"/> collection changes.
      /// </summary>
      protected override void OnDetaching()
      {
          var listView = AssociatedObject;
          if (listView != null)
              RemoveHandler(listView.Items);

          base.OnDetaching();
      }
 }

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If like me you are old and prefer VB.NET then here's Oskars code:

Public Sub AutoSizeColumns()
    Dim gv As GridView = TryCast(Me.listview1.View, GridView)
    If gv IsNot Nothing Then
        For Each c As GridViewColumn In gv.Columns
            If Double.IsNaN(c.Width) Then
                c.Width = c.ActualWidth
            End If
            c.Width = Double.NaN
        Next
    End If
End Sub

This works great in WPF, finally someone has worked this out. Thanks Oskar.

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Isn't there a way to bind to the ActualWidth of the column? Something like :

<GridViewColumn x:Name="column1" Width="{Binding ElementName=column1, Path=ActualWidth}" />

I have tried this and it works only the first time, it seems. No binding error.

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You could measure the longest string in pixels and then adjust the column widths accordingly:

Graphics graphics = this.CreateGraphics();
SizeF textSize = graphics.MeasureString("How long am I?", this.Font);

If you create an algorithm for sizing each column as a ratio of these lengths, you should get a good result.