WPF MVVM：如何GridViewColumn绑定到视图模型收集？
问题描述：
在我看来，我在我的视图模型绑定到的CollectionView一个ListView，比如像这样的：
In my View I got a ListView bound to a CollectionView in my ViewModel, for example like this:
<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，但我希望能够将它们从视图模型改变。我想我得给GridViewColumn收集到视图模型的东西，但什么，以及如何结合？结果
该视图模型不一无所知WPF的，所以我不知道如何在MVVM实现这一点。
Right now these GridViewColumns are fixed, but I'd like to be able to change them from the ViewModel. I'd guess I'll have to bind the GridViewColumn-collection to something in the ViewModel, but what, and how?
The ViewModel does know nothing of WPF, so I got no clue how to achieve this in MVVM.
在这里任何帮助吗？
答
的列属性不是依赖项属性，所以你不能绑定。但是，有可能以创建可以结合在视图模型集合的附加属性。然后，这个附加属性将创建列给你。
The Columns property is not a dependency property, so you can't bind it. However, it might be possible to create an attached property that you could bind to a collection in your ViewModel. This attached property would then create the columns for you.
更新
OK，这里有一个基本的实现...
OK, here's a basic implementation...
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 类不是真的需要，我只加它的清晰度，但任何类型都行（包括匿名类型）。你只需要指定它的属性保存头文本和显示部件名称。
Note that the ColumnDescriptor class is not actually needed, I only added it for clarity, but any type will do (including an anonymous type). You just need to specify which properties hold the header text and display member name.
另外，请记住，它不是完全测试过，所以可能有一些问题解决...
Also, keep in mind that it's not fully tested yet, so there might be a few problems to fix...