Question

我写了一个非常简单的ViewModel Locator：

public static readonly DependencyProperty LocateForProperty =
    DependencyProperty.RegisterAttached("LocateFor", 
    typeof (Object), 
    typeof (ViewModelLocator), 
    new PropertyMetadata(null, OnLocateForChanged));

public static object GetLocateFor(DependencyObject dependencyObject)
{
    return dependencyObject.GetValue(LocateForProperty);
}

public static void SetLocateFor(DependencyObject dependencyObject, Object value)
{
    dependencyObject.SetValue(LocateForProperty, value);
}

private static void OnLocateForChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs eventArgs)
{
    if (dependencyObject != null)
    {
        var viewModelName = dependencyObject.GetType().AssemblyQualifiedName;
        if (! string.IsNullOrEmpty(viewModelName))
        {
            viewModelName = viewModelName.Replace("View", "ViewModel");
            var viewModel = DependencyLocator.GetInstance(Type.GetType(viewModelName));
            if (viewModel != null)
            {
                ((FrameworkElement) dependencyObject).DataContext = viewModel;
            }
        }
    }
}

并像这样使用它：

<vm:ViewModelLocator.LocateFor>
    <Binding RelativeSource="{RelativeSource Self}" />
</vm:ViewModelLocator.LocateFor>

它在运行时工作得很完美但我丢失了设计时间位置。我怀疑是因为我正在使用相对绑定，我尝试将其更改为x:Static，但这不起作用。是否有任何建议的更改可以让我回到Blendability？

编辑：关于DependencyLocator，它是Ninject的静态包装：

using System;
using System.Collections.Generic;

/// <summary>
/// Defines an object that wraps around specific DI containers.
/// </summary>
public static class DependencyLocator
{
    /// <summary>
    /// Gets or Sets the function used for locating a single instance of a specifc type.
    /// </summary>
    public static Func<Type, object> GetInstance;

    /// <summary>
    /// Gets or Sets the function used for locating all instance of a specific type.
    /// </summary>
    public static Func<Type, IEnumerable<object>> GetAllInstances;

    /// <summary>
    /// Gets the implementation of the provided service.
    /// </summary>
    public static T Get<T>()
    {
        return (T)GetInstance(typeof(T));
    }

    /// <summary>
    /// Gets all implementations of the provided service.
    /// </summary>
    public static IEnumerable<T> GetAll<T>()
    {
        return (IEnumerable<T>) GetAllInstances(typeof (T));
    }
}

将在app.xaml中的app_start类中填充。它是出于设计时的目的设计的，如果我使用View的xaml中定义的实例对象创建一个简单的视图模型定位器类，它确实从DependencyLocator获取了正确的值，它只是因为我切换到Dependency Properties这个问题来了。

Answer 1

此代码只是澄清了您要实现的目标：

// Use this to trigger break into debugger when debugging another instance of Visual Studio in order to debug the behaviour at design time.
System.Diagnostics.Debugger.Break();

if (dependencyObject != null)
{
    var view = GetLocateFor( dependencyObject ); // or instead of this access the changed value through the eventargs

    var viewModelName = view.GetType().AssemblyQualifiedName;

    if (! string.IsNullOrEmpty(viewModelName))
    {
        viewModelName = viewModelName.Replace("View", "ViewModel");
        var viewModel = DependencyLocator.GetInstance(Type.GetType(viewModelName));
        if (viewModel != null)
        {
           ((FrameworkElement) view ).DataContext = viewModel;
        }
    }
}

我可以恢复我的可混合性吗？

1 个答案: