GridViewBehaviors.cs

using Microsoft.Xaml.Behaviors;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Controls;
using System.Windows;
 
namespace Vereinsmeisterschaften.Behaviors
{
    public class GridViewBehaviors
    {
        private static Dictionary<GridViewColumn, double> _lastGridViewColumnWidths = new Dictionary<GridViewColumn, double>();

        public static readonly DependencyProperty CollapseableColumnProperty = DependencyProperty.RegisterAttached("CollapseableColumn", typeof(bool), typeof(GridViewBehaviors), new UIPropertyMetadata(false, OnCollapseableColumnChanged));

        public static bool GetCollapseableColumn(DependencyObject obj)
        {
            return (bool)obj.GetValue(CollapseableColumnProperty);
        }

        public static void SetCollapseableColumn(DependencyObject obj, bool value)
        {
            obj.SetValue(CollapseableColumnProperty, value);
        }
 
        private static void OnCollapseableColumnChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
        {
            GridViewColumnHeader header = obj as GridViewColumnHeader;
            if (header == null)
                return;
 
            header.IsVisibleChanged += new DependencyPropertyChangedEventHandler(AdjustWidth);
        }
 
        private static void AdjustWidth(object sender, DependencyPropertyChangedEventArgs e)
        {
            GridViewColumnHeader header = sender as GridViewColumnHeader;
            if (header == null)
                return;
 
            double newWidth = double.NaN;   // NaN = "Auto"
 
            if (header.Visibility == Visibility.Visible)
            {
                if (_lastGridViewColumnWidths.ContainsKey(header.Column))
                {
                    newWidth = _lastGridViewColumnWidths[header.Column];
                }
                else
                {
                    newWidth = header.Column.ActualWidth;
                    _lastGridViewColumnWidths.Add(header.Column, newWidth);
                }
                header.Column.Width = newWidth;
            }
            else
            {
                // Save the current width of the column
                if (header.Column.ActualWidth != 0)
                {
                    if (_lastGridViewColumnWidths.ContainsKey(header.Column))
                    {
                        _lastGridViewColumnWidths[header.Column] = header.Column.ActualWidth;
                    }
                    else
                    {
                        _lastGridViewColumnWidths.Add(header.Column, header.Column.ActualWidth);
                    }
                }
                header.Column.Width = 0;
            }
        }
    }
}