如何使CM视图显示两个子视图中的一个，所有（包括父视图）绑定到同一视图模型？

Question

我在 Caliburn Micro 项目中使用视图模型优先方法。

我有一个视图，比如，EmployeeSearchView，绑定到EmployeeSearchViewModel。它有一个内容区域，应该显示 网格或某些结果数据的列表视图。

我可以公开子视图模型，例如EmployeeSearchResultsViewModel，并使用View.Context附加属性在EmployeeSearchResults.GridView和EmployeeSearchResults.ChildView之间进行选择。但是，我不想要额外的子视图模型;我需要显示的数据属性为EmployeeSearchViewModel。

我喜欢让我的子区域显示与其父视图绑定到同一视图模型的不同视图。可以这样做吗？我试过这个，插入EmployeeSearchView中的相关点：

<ContentControl cal:View.Model="{Binding}" cal:View.Context="{Binding Mode}" Grid.Row="1" />

我在“调试”窗格中看到错误：

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidOperationException: Logical tree depth exceeded while traversing the tree. This could indicate a cycle in the tree.
   at System.Windows.FrameworkElement.FindResourceInTree(FrameworkElement feStart, FrameworkContentElement fceStart, DependencyProperty dp, Object resourceKey, Object unlinkedParent, Boolean allowDeferredResourceReference, Boolean mustReturnDeferredResourceReference, DependencyObject boundaryElement, InheritanceBehavior& inheritanceBehavior, Object& source)
   at System.Windows.FrameworkElement.FindResourceInternal(FrameworkElement fe, FrameworkContentElement fce, DependencyProperty dp, Object resourceKey, Object unlinkedParent, Boolean allowDeferredResourceReference, Boolean mustReturnDeferredResourceReference, DependencyObject boundaryElement, Boolean isImplicitStyleLookup, Object& source)
   at System.Windows.FrameworkElement.FindImplicitStyleResource(FrameworkElement fe, Object resourceKey, Object& source)

CM记录随后表明事情已正确连接，但视图不显示。

Info: Binding MyProject.Views.EmployeeSearchView and MyProject.ViewModels.EmployeeSearchViewModel.
Info: Attaching MyProject.Views.EmployeeSearchView to MyProject.ViewModels.EmployeeSearchViewModel.
Info: Binding MyProject.Views.EmployeeSearch.GridView and MyProject.ViewModels.EmployeeSearchViewModel.
Info: Setting DC of MyProject.Views.EmployeeSearch.GridView to MyProject.ViewModels.EmployeeSearchViewModel.
Info: Attaching message handler MyProject.ViewModels.EmployeeSearchViewModel to MyProject.Views.EmployeeSearch.GridView.

Answer 1

多么干净的想法，我之前没有考虑过像这样构图，而且听起来确实可能。我只是快速尝试使用测试项目，我能够得到你所追求的行为，基本上正是你所描述的。

快速浏览我使用的测试类/ XAML：

TestViewModel.cs

public class TestViewModel
{
    public string TestProperty { get; set; }
    public string AnotherTestProperty { get; set; }
    public string Mode { get; set; }

    public TestViewModel()
    {
        TestProperty = "A Testing String.";
        AnotherTestProperty = "Another Testing String";
        Mode = "Test"; // Hard Coded to my Test Context
    }
}

TestView.xaml

<UserControl x:Class="WpfApplication1.TestView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:cal="http://www.caliburnproject.org"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <StackPanel>
        <TextBlock Text="This is the main TestViewModel I can bind to properties out here:"/>
        <TextBlock x:Name="TestProperty" />
        <TextBlock x:Name="AnotherTestProperty" />
        <ContentControl cal:View.Model="{Binding}" cal:View.Context="{Binding Mode}" Grid.Row="1" />
    </StackPanel>
</Grid>
</UserControl>

Test.xaml

<UserControl x:Class="WpfApplication1.Test.Test"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d">
<Grid Background="#FF2BFB16">
    <StackPanel>
        <TextBlock Text="This is another View, It's also attached to the Test ViewModel."/>
        <TextBlock Text="I can bind to the same properties in here:" />
        <TextBlock x:Name="TestProperty" />
        <TextBlock x:Name="AnotherTestProperty" />
    </StackPanel>
</Grid>

产生这个（远非漂亮）结果：

我认为你走在正确的轨道上，我怀疑问题（基于错误消息）与Mode或View的设计有关。如果我尝试指定不存在的Mode，我会遇到问题，因为快速测试会尝试对Mode的名称进行硬编码。

可能是你的Views之一试图将主EmployeeSearchView组成一个子节点，它本身包含另一个EmployeeSearchView视图，依此类推（View永远无法解析）本身）。