UserControl中嵌套DataGrid中的WPF SelectedItem属性 [英] WPF SelectedItem property in nested DataGrid in UserControl

问题描述

我有 UserControl ，让它称为 CustomDataGrid ，其中包含 DataGrid 。剩下的内容没关系。 SelectedItem 属性 DataGrid 必须是 SelectedItem 属性 CustomDataGrid 。我想要使​​用绑定与此属性，因为我使用 MVVM 模式。所以我必须在 CustomDataGrid 中声明 SelectedItem 作为 DependencyProperty 。但是我没有任何想法，我可以正确地使它...

这是如何 DepedencyProperty -s被声明通常：

  public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.Register（
SelectedItem，typeof（Object），typeof （CustomDataGrid），
 new FrameworkPropertyMetadata（默认（Object），SelectedItemPropertyCallback）
 {
 BindsTwoWayByDefault = true，
 DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged 
}）; 
 
 //可选
 private static void SelectedItemPropertyCallback（DependencyObject obj，DependencyPropertyChangedEventArgs e）
 {
 // dataGrid  - DataGrid嵌套在UserControl
（（CustomDataGrid）obj）.dataGrid.SelectedItem = e.NewValue; 
} 
 
 //显然，它没有与嵌套的dataGrid的任何链接。这就是问题。 
 public Object SelectedItem 
 {
 
 get {return GetValue（SelectedItemProperty）; } 
 set {SetValue（SelectedItemProperty，value）; } 
} 
  

那么，我如何声明 SelectedItem 属性正确？

解决方案

您可以利用绑定框架将这些属性从底层对象连接到外部容器

假设 CustomDataGrid 为 UserControl

< pre class =lang-cs prettyprint-override> class CustomDataGrid：UserControl
{
public CustomDataGrid（）
{
Binding b = new Binding SelectedItem）;
b.Source = this;
b.Mode = BindingMode.TwoWay;
dataGrid.SetBinding（DataGrid.SelectedItemProperty，b）;
}

public object SelectedItem
{
get {return（object）GetValue（SelectedItemProperty）; }
set {SetValue（SelectedItemProperty，value）; }
}

//使用DependencyProperty作为SelectedItem的后备存储。这使得动画，样式，绑定等...
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.Register（SelectedItem，typeof（object），typeof（CustomDataGrid），new PropertyMetadata（null）） ;
}


我创建了一个名为 SelectedItem 在 CustomDataGrid 中，并设置一个双向绑定到 SelectedItem 的实际 dataGrid

所以这将连接这些属性，并将来回传播任何更改。

I have UserControl, lets call it as CustomDataGrid, that contains DataGrid. Remained content doesn't matter. SelectedItem property of DataGrid must be SelectedItem property of CustomDataGrid. And I wanna be able to use Binding with this property, cause I use MVVM pattern. So I have to declare SelectedItem as DependencyProperty in CustomDataGrid. But I have no ideas haw can I make it properly...

This is how DepedencyProperty-s is declared usually:

public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.Register(
        "SelectedItem", typeof(Object), typeof(CustomDataGrid),
        new FrameworkPropertyMetadata(default(Object), SelectedItemPropertyCallback)
        {
            BindsTwoWayByDefault = true, 
            DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
        });

// Optionally
private static void SelectedItemPropertyCallback(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
    // dataGrid - `DataGrid` nested in `UserControl` 
    ((CustomDataGrid)obj).dataGrid.SelectedItem = e.NewValue;
}

// Obviously, it has no any link with nested `dataGrid`. This is the problem.  
public Object SelectedItem
{

    get { return GetValue(SelectedItemProperty); }
    set { SetValue(SelectedItemProperty, value); }
}

So, how can I declare SelectedItem property correctly?

解决方案

You could leverage the binding framework for wiring such properties from underlying objects to outer containers

example assuming CustomDataGrid as UserControl

        class CustomDataGrid : UserControl
        {
            public CustomDataGrid()
            {
                Binding b = new Binding("SelectedItem");
                b.Source = this;
                b.Mode = BindingMode.TwoWay;
                dataGrid.SetBinding(DataGrid.SelectedItemProperty, b);
            }

            public object SelectedItem
            {
                get { return (object)GetValue(SelectedItemProperty); }
                set { SetValue(SelectedItemProperty, value); }
            }

            // Using a DependencyProperty as the backing store for SelectedItem.  This enables animation, styling, binding, etc...
            public static readonly DependencyProperty SelectedItemProperty =
                DependencyProperty.Register("SelectedItem", typeof(object), typeof(CustomDataGrid), new PropertyMetadata(null));
        }

I have created a property called SelectedItem in CustomDataGrid and set a two way binding to SelectedItem of the actual dataGrid inside.

so this will wire up these properties and will propagate any changes to and fro.

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