WPF MVVM:如何将 GridViewColumn 绑定到 ViewModel-Collection? [英] WPF MVVM: how to bind GridViewColumn to ViewModel-Collection?
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问题描述
在我的视图中，我将一个 ListView 绑定到了我的 ViewModel 中的 CollectionView，例如像这样:
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，但我希望能够从 ViewModel 更改它们.我想我必须将 GridViewColumn 集合绑定到 ViewModel 中的某些内容，但是是什么，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.
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.
这里有什么帮助吗?
推荐答案
Columns 属性不是依赖属性，因此您无法绑定它.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.
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
好的，这是一个基本的实现...
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 类实际上并不需要，我添加它只是为了清楚起见，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和显示成员名称.
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，它还没有经过全面测试，所以可能有一些问题需要解决......
Also, keep in mind that it's not fully tested yet, so there might be a few problems to fix...
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