Question

我有一个ViewModel的ObservableCollection，我想绑定到包含相关子视图的ItemsControl。当我将ViewModels添加到我的集合中时，ItemsControl中会生成适当数量的子视图。但是，每个生成的视图的DataContext都为null。如果我内联我的子视图，它可以正常工作。那么，我需要做什么才能将我的子视图的DataContext设置为我的ViewModels？

这是我的父ViewModel中的相关位：

    public ObservableCollection<ChildViewModel> Numbers { get; set; }

    public ParentViewModel()
    {
        Numbers = new ObservableCollection<ChildViewModel>();
    }

    private void ShowNumbers()
    {
        foreach (var num in Enumerable.Range(0, number))
        {
            var childView = new ChildViewModel(number.ToString());
            Numbers.Add(childView);
        }
    }

父视图中的相关位：

        <ItemsControl ItemsSource="{Binding Numbers, UpdateSourceTrigger=PropertyChanged}">
            <ItemsControl.ItemTemplate>
                <DataTemplate DataType="{x:Type vm:ChildViewModel}">
                    <v:ChildView />
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>

儿童观点：

<UserControl x:Class="TestWpfApp.Views.ChildView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:prism="http://prismlibrary.com/"             
         prism:ViewModelLocator.AutoWireViewModel="True">
<Grid>
    <Label Content="{Binding NumberString}" Width="30" Height="30" BorderThickness="1" BorderBrush="Black" HorizontalAlignment="Center"/>
</Grid>
</UserControl>

Child ViewModel：

public class ChildViewModel : BindableBase
{
    private string numberString;
    public string NumberString
    {
        get
        {
            return numberString;
        }
        set
        {
            SetProperty(ref numberString, value);
        }
    }

    public ChildViewModel() { }

    public ChildViewModel(string number)
    {
        NumberString = number;
    }
}

显然，我有一些错误的配置，但我不能为我的生活找出什么。

仅供参考我正在使用棱镜库

Answer 1

WPF会自动将DataContext中的项容器元素的ItemsControl设置为相应的项目实例，以便它可以继承到ItemTemplate。显然，当您设置prism:ViewModelLocator.AutoWireViewModel属性时，此机制将被禁用。

所以，只需将它从您的ChildView的XAML中删除：

<UserControl x:Class="TestWpfApp.Views.ChildView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:prism="http://prismlibrary.com/">
    <Grid>
        <Label Content="{Binding NumberString}" Width="30" Height="30"
               BorderThickness="1" BorderBrush="Black" HorizontalAlignment="Center" />
    </Grid>
</UserControl>

作为一般规则，UserControl永远不应该直接或通过像DataContext之类的机制显式设置自己的AutoWireViewModel，因为这有效地阻止了从其父控件继承DataContext

Answer 2

在ItemsControl中生成适当数量的子视图。
因此可以得出结论，DataContext已正确设置为viewModel，但未应用DataTemplate's。

我有同样的问题，我也在使用Prism库。我想分享一下如何做到这一点的方式。也许对你有帮助。我用CompositeCollection：

<强>视图模型：

public class MainWindowVM:ViewModelBase
{
    public MainWindowVM()
    {
        LoadData();
    }
    private void LoadData()
    {            
        ObservableCollection<Human> coll = new ObservableCollection<Human>();
        for (int indexLoop = 0; indexLoop < 5; indexLoop++)
        {
            if (indexLoop % 2 == 0)
            {
                coll.Add(new Sportsman() {FirstName=indexLoop.ToString(), LastName=indexLoop.ToString()});
            }
            else
            {
                coll.Add(new Employee() { FirstName = indexLoop.ToString(), LastName = indexLoop.ToString()});
            }                
        }
        CompositeCollection compositeColl = new CompositeCollection();
        compositeColl.Add(new CollectionContainer() { Collection = coll });
        FooData = compositeColl;
    }

    private CompositeCollection fooData;

    public CompositeCollection FooData
    {
        get { return fooData; }
        set
        {
            fooData = value;
        }
    }

}

<强>型号：

public class Human
{        
    private string firstName;
    public string FirstName
    {
        get { return firstName; }
        set { firstName = value; }
    }

    private string lastName;
    public string LastName
    {
        get { return lastName; }
        set { lastName = value; }
    }
}

public class Sportsman:Human
{    }

public class Employee:Human
{    }

查看：

<Window x:Class="ItemsControlWithDataTemplates.MainWindow"  Title="MainWindow" Height="350" Width="525"> <Window.DataContext> <vm:MainWindowVM/> </Window.DataContext> <Grid> <ItemsControl ItemsSource="{Binding FooData}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <VirtualizingStackPanel/> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> <ItemsControl.Resources> <DataTemplate DataType="{x:Type model:Employee}"> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding FirstName}"/> <TextBlock Text=" ( Employee"/> <TextBlock Text="{Binding LastName}"/> <TextBlock Text=")"/> </StackPanel> </DataTemplate> <DataTemplate DataType="{x:Type model:Sportsman}"> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding FirstName}"/> <TextBlock Text=" - Sportsman "/> <TextBlock Text="{Binding LastName}"/> </StackPanel> </DataTemplate> <DataTemplate DataType="{x:Type model:Human}"> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding FirstName}"/> <TextBlock Text=" - "/> <TextBlock Text="{Binding LastName}"/> </StackPanel> </DataTemplate> </ItemsControl.Resources> </ItemsControl> </Grid> </Window>

实际上我在DataContext应用程序中以下列方式设置了Prism：

public MyUserControl(IMyViewModel viewModel) { InitializeComponent(); DataContext = viewModel; }

在ItemsControl中使用View as DataTemplate时未设置DataContext

2 个答案: