WPF MVVM：如何将 GridViewColumn 绑定到 ViewModel-Collection？

Question

在我的视图中，我有一个 ListView 绑定到我的 ViewModel 中的 CollectionView，例如：

<ListView ItemsSource="{Binding MyCollection}" IsSynchronizedWithCurrentItem="true">
  <ListView.View>
    <GridView>
      <GridViewColumn Header="Title" DisplayMemberBinding="{Binding Path=Title}"/>
      <GridViewColumn Header="Name" DisplayMemberBinding="{Binding Path=Name}"/>
      <GridViewColumn Header="Phone" DisplayMemberBinding="{Binding Path=Phone}"/>
      <GridViewColumn Header="E-mail" DisplayMemberBinding="{Binding Path=EMail}"/>
    </GridView>
  </ListView.View>
</ListView>

现在这些 GridViewColumns 是固定的，但我希望能够从 ViewModel 更改它们。我想我必须将 GridViewColumn-collection 绑定到 ViewModel 中的某些东西，但是什么，以及如何？
ViewModel 对 WPF 一无所知，所以我不知道如何在 MVVM 中实现这一点。

这里有什么帮助吗？

Answer 1

Columns 属性不是依赖属性，所以不能绑定它。但是，可以创建一个附加属性，您可以将其绑定到 ViewModel 中的集合。然后，此附加属性将为您创建列。

---

更新

好的，这是一个基本的实现......

附加属性

using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

namespace TestPadWPF
{
    public static class GridViewColumns
    {
        [AttachedPropertyBrowsableForType(typeof(GridView))]
        public static object GetColumnsSource(DependencyObject obj)
        {
            return (object)obj.GetValue(ColumnsSourceProperty);
        }

        public static void SetColumnsSource(DependencyObject obj, object value)
        {
            obj.SetValue(ColumnsSourceProperty, value);
        }

        // Using a DependencyProperty as the backing store for ColumnsSource.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty ColumnsSourceProperty =
            DependencyProperty.RegisterAttached(
                "ColumnsSource",
                typeof(object),
                typeof(GridViewColumns),
                new UIPropertyMetadata(
                    null,
                    ColumnsSourceChanged));


        [AttachedPropertyBrowsableForType(typeof(GridView))]
        public static string GetHeaderTextMember(DependencyObject obj)
        {
            return (string)obj.GetValue(HeaderTextMemberProperty);
        }

        public static void SetHeaderTextMember(DependencyObject obj, string value)
        {
            obj.SetValue(HeaderTextMemberProperty, value);
        }

        // Using a DependencyProperty as the backing store for HeaderTextMember.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty HeaderTextMemberProperty =
            DependencyProperty.RegisterAttached("HeaderTextMember", typeof(string), typeof(GridViewColumns), new UIPropertyMetadata(null));


        [AttachedPropertyBrowsableForType(typeof(GridView))]
        public static string GetDisplayMemberMember(DependencyObject obj)
        {
            return (string)obj.GetValue(DisplayMemberMemberProperty);
        }

        public static void SetDisplayMemberMember(DependencyObject obj, string value)
        {
            obj.SetValue(DisplayMemberMemberProperty, value);
        }

        // Using a DependencyProperty as the backing store for DisplayMember.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty DisplayMemberMemberProperty =
            DependencyProperty.RegisterAttached("DisplayMemberMember", typeof(string), typeof(GridViewColumns), new UIPropertyMetadata(null));


        private static void ColumnsSourceChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
        {
            GridView gridView = obj as GridView;
            if (gridView != null)
            {
                gridView.Columns.Clear();

                if (e.OldValue != null)
                {
                    ICollectionView view = CollectionViewSource.GetDefaultView(e.OldValue);
                    if (view != null)
                        RemoveHandlers(gridView, view);
                }

                if (e.NewValue != null)
                {
                    ICollectionView view = CollectionViewSource.GetDefaultView(e.NewValue);
                    if (view != null)
                    {
                        AddHandlers(gridView, view);
                        CreateColumns(gridView, view);
                    }
                }
            }
        }

        private static IDictionary<ICollectionView, List<GridView>> _gridViewsByColumnsSource =
            new Dictionary<ICollectionView, List<GridView>>();

        private static List<GridView> GetGridViewsForColumnSource(ICollectionView columnSource)
        {
            List<GridView> gridViews;
            if (!_gridViewsByColumnsSource.TryGetValue(columnSource, out gridViews))
            {
                gridViews = new List<GridView>();
                _gridViewsByColumnsSource.Add(columnSource, gridViews);
            }
            return gridViews;
        }

        private static void AddHandlers(GridView gridView, ICollectionView view)
        {
            GetGridViewsForColumnSource(view).Add(gridView);
            view.CollectionChanged += ColumnsSource_CollectionChanged;
        }

        private static void CreateColumns(GridView gridView, ICollectionView view)
        {
            foreach (var item in view)
            {
                GridViewColumn column = CreateColumn(gridView, item);
                gridView.Columns.Add(column);
            }
        }

        private static void RemoveHandlers(GridView gridView, ICollectionView view)
        {
            view.CollectionChanged -= ColumnsSource_CollectionChanged;
            GetGridViewsForColumnSource(view).Remove(gridView);
        }

        private static void ColumnsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            ICollectionView view = sender as ICollectionView;
            var gridViews = GetGridViewsForColumnSource(view);
            if (gridViews == null || gridViews.Count == 0)
                return;

            switch (e.Action)
            {
                case NotifyCollectionChangedAction.Add:
                    foreach (var gridView in gridViews)
                    {
                        for (int i = 0; i < e.NewItems.Count; i++)
                        {
                            GridViewColumn column = CreateColumn(gridView, e.NewItems[i]);
                            gridView.Columns.Insert(e.NewStartingIndex + i, column);
                        }
                    }
                    break;
                case NotifyCollectionChangedAction.Move:
                    foreach (var gridView in gridViews)
                    {
                        List<GridViewColumn> columns = new List<GridViewColumn>();
                        for (int i = 0; i < e.OldItems.Count; i++)
                        {
                            GridViewColumn column = gridView.Columns[e.OldStartingIndex + i];
                            columns.Add(column);
                        }
                        for (int i = 0; i < e.NewItems.Count; i++)
                        {
                            GridViewColumn column = columns[i];
                            gridView.Columns.Insert(e.NewStartingIndex + i, column);
                        }
                    }
                    break;
                case NotifyCollectionChangedAction.Remove:
                    foreach (var gridView in gridViews)
                    {
                        for (int i = 0; i < e.OldItems.Count; i++)
                        {
                            gridView.Columns.RemoveAt(e.OldStartingIndex);
                        }
                    }
                    break;
                case NotifyCollectionChangedAction.Replace:
                    foreach (var gridView in gridViews)
                    {
                        for (int i = 0; i < e.NewItems.Count; i++)
                        {
                            GridViewColumn column = CreateColumn(gridView, e.NewItems[i]);
                            gridView.Columns[e.NewStartingIndex + i] = column;
                        }
                    }
                    break;
                case NotifyCollectionChangedAction.Reset:
                    foreach (var gridView in gridViews)
                    {
                        gridView.Columns.Clear();
                        CreateColumns(gridView, sender as ICollectionView);
                    }
                    break;
                default:
                    break;
            }
        }

        private static GridViewColumn CreateColumn(GridView gridView, object columnSource)
        {
            GridViewColumn column = new GridViewColumn();
            string headerTextMember = GetHeaderTextMember(gridView);
            string displayMemberMember = GetDisplayMemberMember(gridView);
            if (!string.IsNullOrEmpty(headerTextMember))
            {
                column.Header = GetPropertyValue(columnSource, headerTextMember);
            }
            if (!string.IsNullOrEmpty(displayMemberMember))
            {
                string propertyName = GetPropertyValue(columnSource, displayMemberMember) as string;
                column.DisplayMemberBinding = new Binding(propertyName);
            }
            return column;
        }

        private static object GetPropertyValue(object obj, string propertyName)
        {
            if (obj != null)
            {
                PropertyInfo prop = obj.GetType().GetProperty(propertyName);
                if (prop != null)
                    return prop.GetValue(obj, null);
            }
            return null;
        }
    }
}

视图模型

class PersonsViewModel
{
    public PersonsViewModel()
    {
        this.Persons = new ObservableCollection<Person>
        {
            new Person
            {
                Name = "Doe",
                FirstName = "John",
                DateOfBirth = new DateTime(1981, 9, 12)
            },
            new Person
            {
                Name = "Black",
                FirstName = "Jack",
                DateOfBirth = new DateTime(1950, 1, 15)
            },
            new Person
            {
                Name = "Smith",
                FirstName = "Jane",
                DateOfBirth = new DateTime(1987, 7, 23)
            }
        };

        this.Columns = new ObservableCollection<ColumnDescriptor>
        {
            new ColumnDescriptor { HeaderText = "Last name", DisplayMember = "Name" },
            new ColumnDescriptor { HeaderText = "First name", DisplayMember = "FirstName" },
            new ColumnDescriptor { HeaderText = "Date of birth", DisplayMember = "DateOfBirth" }
        };
    }

    public ObservableCollection<Person> Persons { get; private set; }

    public ObservableCollection<ColumnDescriptor> Columns { get; private set; }

    private ICommand _addColumnCommand;
    public ICommand AddColumnCommand
    {
        get
        {
            if (_addColumnCommand == null)
            {
                _addColumnCommand = new DelegateCommand<string>(
                    s =>
                    {
                        this.Columns.Add(new ColumnDescriptor { HeaderText = s, DisplayMember = s });
                    });
            }
            return _addColumnCommand;
        }
    }

    private ICommand _removeColumnCommand;
    public ICommand RemoveColumnCommand
    {
        get
        {
            if (_removeColumnCommand == null)
            {
                _removeColumnCommand = new DelegateCommand<string>(
                    s =>
                    {
                        this.Columns.Remove(this.Columns.FirstOrDefault(d => d.DisplayMember == s));
                    });
            }
            return _removeColumnCommand;
        }
    }
}

XAML：

    <ListView ItemsSource="{Binding Persons}" Grid.Row="0">
        <ListView.View>
            <GridView local:GridViewColumns.HeaderTextMember="HeaderText"
                      local:GridViewColumns.DisplayMemberMember="DisplayMember"
                      local:GridViewColumns.ColumnsSource="{Binding Columns}"/>
        </ListView.View>
    </ListView>

请注意，ColumnDescriptor 类实际上并不需要，我只是为了清楚起见添加了它，但任何类型都可以（包括匿名类型）。您只需要指定哪些属性保存标题文本并显示成员名称。

另外，请记住，它尚未经过全面测试，因此可能需要修复一些问题...

Answer 2

我采用了 Thomas Levesque 的出色解决方案并对其进行了修改，以删除 GridViews 的静态集合，并添加了设置列宽和字符串格式的功能，所以我想分享我的代码。

修改后的附加属性类：

public static class GridViewColumnCollection
{
    public static readonly DependencyProperty ColumnCollectionBehaviourProperty =
        DependencyProperty.RegisterAttached("ColumnCollectionBehaviour", typeof(GridViewColumnCollectionBehaviour), typeof(GridViewColumnCollection), new UIPropertyMetadata(null));

    public static readonly DependencyProperty ColumnsSourceProperty =
        DependencyProperty.RegisterAttached("ColumnsSource", typeof(object), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.ColumnsSourceChanged));

    public static readonly DependencyProperty DisplayMemberFormatMemberProperty =
        DependencyProperty.RegisterAttached("DisplayMemberFormatMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.DisplayMemberFormatMemberChanged));

    public static readonly DependencyProperty DisplayMemberMemberProperty =
        DependencyProperty.RegisterAttached("DisplayMemberMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.DisplayMemberMemberChanged));

    public static readonly DependencyProperty HeaderTextMemberProperty =
        DependencyProperty.RegisterAttached("HeaderTextMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.HeaderTextMemberChanged));

    public static readonly DependencyProperty WidthMemberProperty =
        DependencyProperty.RegisterAttached("WidthMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.WidthMemberChanged));

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static GridViewColumnCollectionBehaviour GetColumnCollectionBehaviour(DependencyObject obj)
    {
        return (GridViewColumnCollectionBehaviour)obj.GetValue(ColumnCollectionBehaviourProperty);
    }

    public static void SetColumnCollectionBehaviour(DependencyObject obj, GridViewColumnCollectionBehaviour value)
    {
        obj.SetValue(ColumnCollectionBehaviourProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static object GetColumnsSource(DependencyObject obj)
    {
        return (object)obj.GetValue(ColumnsSourceProperty);
    }

    public static void SetColumnsSource(DependencyObject obj, object value)
    {
        obj.SetValue(ColumnsSourceProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetDisplayMemberFormatMember(DependencyObject obj)
    {
        return (string)obj.GetValue(DisplayMemberFormatMemberProperty);
    }

    public static void SetDisplayMemberFormatMember(DependencyObject obj, string value)
    {
        obj.SetValue(DisplayMemberFormatMemberProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetDisplayMemberMember(DependencyObject obj)
    {
        return (string)obj.GetValue(DisplayMemberMemberProperty);
    }

    public static void SetDisplayMemberMember(DependencyObject obj, string value)
    {
        obj.SetValue(DisplayMemberMemberProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetHeaderTextMember(DependencyObject obj)
    {
        return (string)obj.GetValue(HeaderTextMemberProperty);
    }

    public static void SetHeaderTextMember(DependencyObject obj, string value)
    {
        obj.SetValue(HeaderTextMemberProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetWidthMember(DependencyObject obj)
    {
        return (string)obj.GetValue(WidthMemberProperty);
    }

    public static void SetWidthMember(DependencyObject obj, string value)
    {
        obj.SetValue(WidthMemberProperty, value);
    }

    private static void ColumnsSourceChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).ColumnsSource = e.NewValue;
    }

    private static void DisplayMemberFormatMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).DisplayMemberFormatMember = e.NewValue as string;
    }

    private static void DisplayMemberMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).DisplayMemberMember = e.NewValue as string;
    }

    private static void HeaderTextMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).HeaderTextMember = e.NewValue as string;
    }

    private static void WidthMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).WidthMember = e.NewValue as string;
    }

    private static GridViewColumnCollectionBehaviour GetOrCreateColumnCollectionBehaviour(DependencyObject source)
    {
        GridViewColumnCollectionBehaviour behaviour = GetColumnCollectionBehaviour(source);

        if (behaviour == null)
        {
            GridView typedSource = source as GridView;

            if (typedSource == null)
            {
                throw new Exception("This property can only be set on controls deriving GridView");
            }

            behaviour = new GridViewColumnCollectionBehaviour(typedSource);

            SetColumnCollectionBehaviour(typedSource, behaviour);
        }

        return behaviour;
    }
}

行为（这是针对每个 GridView 存储的，无需集中存储集合-GridView 映射）：

public class GridViewColumnCollectionBehaviour
{
    private object columnsSource;
    private GridView gridView;

    public GridViewColumnCollectionBehaviour(GridView gridView)
    {
        this.gridView = gridView;
    }

    public object ColumnsSource
    {
        get { return this.columnsSource; }
        set
        {
            object oldValue = this.columnsSource;
            this.columnsSource = value;
            this.ColumnsSourceChanged(oldValue, this.columnsSource);
        }
    }

    public string DisplayMemberFormatMember { get; set; }

    public string DisplayMemberMember { get; set; }

    public string HeaderTextMember { get; set; }

    public string WidthMember { get; set; }

    private void AddHandlers(ICollectionView collectionView)
    {
        collectionView.CollectionChanged += this.ColumnsSource_CollectionChanged;
    }

    private void ColumnsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        ICollectionView view = sender as ICollectionView;

        if (this.gridView == null)
        {
            return;
        }

        switch (e.Action)
        {
            case NotifyCollectionChangedAction.Add:
                for (int i = 0; i < e.NewItems.Count; i++)
                {
                    GridViewColumn column = CreateColumn(e.NewItems[i]);
                    gridView.Columns.Insert(e.NewStartingIndex + i, column);
                }
                break;
            case NotifyCollectionChangedAction.Move:
                List<GridViewColumn> columns = new List<GridViewColumn>();

                for (int i = 0; i < e.OldItems.Count; i++)
                {
                    GridViewColumn column = gridView.Columns[e.OldStartingIndex + i];
                    columns.Add(column);
                }

                for (int i = 0; i < e.NewItems.Count; i++)
                {
                    GridViewColumn column = columns[i];
                    gridView.Columns.Insert(e.NewStartingIndex + i, column);
                }
                break;
            case NotifyCollectionChangedAction.Remove:
                for (int i = 0; i < e.OldItems.Count; i++)
                {
                    gridView.Columns.RemoveAt(e.OldStartingIndex);
                }
                break;
            case NotifyCollectionChangedAction.Replace:
                for (int i = 0; i < e.NewItems.Count; i++)
                {
                    GridViewColumn column = CreateColumn(e.NewItems[i]);

                    gridView.Columns[e.NewStartingIndex + i] = column;
                }
                break;
            case NotifyCollectionChangedAction.Reset:
                gridView.Columns.Clear();
                CreateColumns(sender as ICollectionView);
                break;
            default:
                break;
        }
    }

    private void ColumnsSourceChanged(object oldValue, object newValue)
    {
        if (this.gridView != null)
        {
            gridView.Columns.Clear();

            if (oldValue != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(oldValue);

                if (view != null)
                {
                    this.RemoveHandlers(view);
                }
            }

            if (newValue != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(newValue);

                if (view != null)
                {
                    this.AddHandlers(view);

                    this.CreateColumns(view);
                }
            }
        }
    }

    private GridViewColumn CreateColumn(object columnSource)
    {
        GridViewColumn column = new GridViewColumn();

        if (!string.IsNullOrEmpty(this.HeaderTextMember))
        {
            column.Header = GetPropertyValue(columnSource, this.HeaderTextMember);
        }

        if (!string.IsNullOrEmpty(this.DisplayMemberMember))
        {
            string propertyName = GetPropertyValue(columnSource, this.DisplayMemberMember) as string;

            string format = null;

            if (!string.IsNullOrEmpty(this.DisplayMemberFormatMember))
            {
                format = GetPropertyValue(columnSource, this.DisplayMemberFormatMember) as string;
            }

            if (string.IsNullOrEmpty(format))
            {
                format = "{0}";
            }

            column.DisplayMemberBinding = new Binding(propertyName) { StringFormat = format };
        }

        if (!string.IsNullOrEmpty(this.WidthMember))
        {
            double width = (double)GetPropertyValue(columnSource, this.WidthMember);
            column.Width = width;
        }

        return column;
    }

    private void CreateColumns(ICollectionView collectionView)
    {
        foreach (object item in collectionView)
        {
            GridViewColumn column = this.CreateColumn(item);

            this.gridView.Columns.Add(column);
        }
    }

    private object GetPropertyValue(object obj, string propertyName)
    {
        object returnVal = null;

        if (obj != null)
        {
            PropertyInfo prop = obj.GetType().GetProperty(propertyName);

            if (prop != null)
            {
                returnVal = prop.GetValue(obj, null);
            }
        }

        return returnVal;
    }

    private void RemoveHandlers(ICollectionView collectionView)
    {
        collectionView.CollectionChanged -= this.ColumnsSource_CollectionChanged;
    }
}

Answer 3

我认为这段代码会导致一些内存泄漏问题；正如您的类 GridViewColumns 所述，您已经定义了一个静态字典“_gridViewsByColumnsSource”，其中包含网格视图及其列源引用；所以这是对添加的网格视图和列源的强烈参考；因为这个字典是静态的，所以似乎一直有一个静态引用“指向”gridviews和columns源数据，如果gridview定义的屏幕关闭，则启动GC时gridview无法被GC收集；随着打开的类似屏幕越来越多，越来越多的gridview和它的columns源数据无法采集，最后会出现内存泄漏。