Prism Step4 ViewModelLocationProvider
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Prism Step4 ViewModelLocationProvider

ViewModel 是对应的 View（数据和行为）的抽象，View 只是 ViewModel 的一个消费者，那么还有其他的消费者吗？当然有了，那就是单元测试（Unit Test），这个后面说。ViewModel 为 View 提供数据上下文（DataContext），简单的说，你 View 需要展示的东西，都在我这里，你需要跟我绑定，包括数据和命令，Prism 提供了自动的 ViewModel 匹配。

约定的绑定方式

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using Prism.Ioc;
using Prism.Unity;
using System.Windows;
using ViewModelLocator.Views;

namespace ViewModelLocator
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : PrismApplication
    {
        protected override Window CreateShell()
        {
            return Container.Resolve<MainWindow>();
        }

        protected override void RegisterTypes(IContainerRegistry containerRegistry)
        {

        }
    }
}

ViewModel

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using Prism.Mvvm;

namespace ViewModelLocator.ViewModels
{
    public class MainWindowViewModel : BindableBase
    {
        private string _title = "Prism Unity Application";
        public string Title
        {
            get { return _title; }
            set { SetProperty(ref _title, value); }
        }

        public MainWindowViewModel()
        {

        }
    }
}

View 视图

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<Window x:Class="ViewModelLocator.Views.MainWindow"
        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"

        Title="{Binding Title}" Height="350" Width="525">
    <Grid>
        <ContentControl prism:RegionManager.RegionName="ContentRegion" />
    </Grid>
</Window>

正常的绑定

方式 1

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<UserControl.DataContext>
    <vm:NumberChangeLogViewModel />
</UserControl.DataContext>

方式 2

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<vw:NumberView
    DockPanel.Dock="Top"
    DataContext="{Binding Path=Number, Mode=OneTime}" />

Prism 源码

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/// <summary>
/// ViewModelfactory that provides the View instance and ViewModel type as parameters.
/// </summary>
static Func<object, Type, object> _defaultViewModelFactoryWithViewParameter;

/// <summary>
/// Default view type to view model type resolver, assumes the view model is in same assembly as the view type, but in the "ViewModels" namespace.
/// </summary>
static Func<Type, Type> _defaultViewTypeToViewModelTypeResolver =
    viewType =>
    {
        var viewName = viewType.FullName;
        viewName = viewName.Replace(".Views.", ".ViewModels.");
        var viewAssemblyName = viewType.GetTypeInfo().Assembly.FullName;
        var suffix = viewName.EndsWith("View") ? "Model" : "ViewModel";
        var viewModelName = String.Format(CultureInfo.InvariantCulture, "{0}{1}, {2}", viewName, suffix, viewAssemblyName);
        return Type.GetType(viewModelName);
    };

自定义约束

约定就是要来被打破的，有人可能觉得后缀加一个 ViewModel 实在是不太完美，但是可以改变吗？ 当然可以。

prism 为我们提供了一个可重写的 ConfigureViewModelLocator 的方法来配置 ViewModel 的定位器，如果你想修改默认的约定为 View 的名字后面+VM，你可以在 app.xaml.cs 这样写：

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protected override void ConfigureViewModelLocator()
        {
            base.ConfigureViewModelLocator();

            ViewModelLocationProvider.SetDefaultViewTypeToViewModelTypeResolver((viewType) =>
            {
                var viewName = viewType.FullName;
                var viewAssemblyName = viewType.GetTypeInfo().Assembly.FullName;
                var viewModelName = $"{viewName}VM, {viewAssemblyName}";
                return Type.GetType(viewModelName);
            });
        }

如果你想指定你绑定的 ViewModel 对象又不想遵循一定的规则，你同样可以在 ConfigureViewModelLocator 方法中注册绑定，像下面这样：

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protected override void ConfigureViewModelLocator()
        {
            base.ConfigureViewModelLocator();

            // type / type
            ViewModelLocationProvider.Register(typeof(MainWindow).ToString(), typeof(CustomViewModel));

            // type / factory
            ViewModelLocationProvider.Register(typeof(MainWindow).ToString(), () => Container.Resolve<CustomViewModel>());

            // generic factory
            ViewModelLocationProvider.Register<MainWindow>(() => Container.Resolve<CustomViewModel>());

            // generic type
            ViewModelLocationProvider.Register<MainWindow, CustomViewModel>();
        }
#

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