带有 MVVM ViewModel 的 WPF 用户控件数据绑定(bind)

Question

我在这方面花了很长时间，所以寻求帮助。

使用 mvvm light 与用户控件进行简单数据绑定(bind)不起作用。

我做了以下事情。

使用 VS 2015 创建了一个 MvvmLight (WPF451) 项目并将其命名为 WpfDataBindingUserControlT1

添加了一个 UserControl 并将其重命名为 SimpleUserControl.xaml

在 SimpleUserControl.xaml 中的网格中添加了一些标签作为子项(包含在堆栈面板中)(所有代码在下面给出)

在 SimpleUserControl.xaml(SimpleUserControl.cs) 后面的代码中添加了一个依赖属性，以便这些属性可以帮助我进行数据绑定(bind)。

数据绑定(bind)根本不起作用。我已经拉了一半的头发，所以请帮忙。我想我在这方面很简单。

代码如下。

MainWindows.xaml

<Window x:Class="WpfDataBindingUserControlT1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:ignore="http://www.galasoft.ch/ignore"
        xmlns:local="clr-namespace:WpfDataBindingUserControlT1"
        mc:Ignorable="d ignore"
        Height="400"
        Width="300"
        Title="MVVM Light Application"
        DataContext="{Binding Main, Source={StaticResource Locator}}">

    <Window.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Skins/MainSkin.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Window.Resources>

    <Grid x:Name="LayoutRoot">

        <TextBlock FontSize="36"
                   FontWeight="Bold"
                   Foreground="Purple"
                   Text="{Binding WelcomeTitle}"
                   VerticalAlignment="Center"
                   HorizontalAlignment="Center"
                   TextWrapping="Wrap" />

        <local:SimpleUserControl DataContext="{Binding RelativeSource={RelativeSource Self}}" CellValue="{Binding WelcomeTitle}" />
    </Grid>
</Window>

MainWindow.cs(我没有更改此文件中的任何内容。)

using System.Windows;
using WpfDataBindingUserControlT1.ViewModel;

namespace WpfDataBindingUserControlT1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        /// <summary>
        /// Initializes a new instance of the MainWindow class.
        /// </summary>
        public MainWindow()
        {
            InitializeComponent();
            Closing += (s, e) => ViewModelLocator.Cleanup();
        }
    }
}

简单用户控件.xaml

<UserControl x:Class="WpfDataBindingUserControlT1.SimpleUserControl"
             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:local="clr-namespace:WpfDataBindingUserControlT1"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <StackPanel>
            <Label Content="This Prints" />
            <Label Name="MyLable" Content="{Binding Path=CellValue}"></Label>
            <Label Content="This also Prints" />
        </StackPanel>
    </Grid>
</UserControl>

SimpleUserControl.cs(添加了依赖项)

using System.Windows;
using System.Windows.Controls;

namespace WpfDataBindingUserControlT1
{
    /// <summary>
    /// Interaction logic for SimpleUserControl.xaml
    /// </summary>
    public partial class SimpleUserControl : UserControl
    {
        public string CellValue
        {
            get { return (string)GetValue(CellValueProperty); }
            set { SetValue(CellValueProperty, value); }
        }

        public static readonly DependencyProperty CellValueProperty = 
            DependencyProperty.Register("CellValue", typeof(string), typeof(SimpleUserControl), new FrameworkPropertyMetadata
            {
                BindsTwoWayByDefault = true,
            });

        public SimpleUserControl()
        {
            InitializeComponent();
        }
    }
}

MainViewModel.cs(我没有改变任何东西)

using GalaSoft.MvvmLight;
using WpfDataBindingUserControlT1.Model;

namespace WpfDataBindingUserControlT1.ViewModel
{
    /// <summary>
    /// This class contains properties that the main View can data bind to.
    /// <para>
    /// See http://www.mvvmlight.net
    /// </para>
    /// </summary>
    public class MainViewModel : ViewModelBase
    {
        private readonly IDataService _dataService;

        /// <summary>
        /// The <see cref="WelcomeTitle" /> property's name.
        /// </summary>
        public const string WelcomeTitlePropertyName = "WelcomeTitle";

        private string _welcomeTitle = string.Empty;

        /// <summary>
        /// Gets the WelcomeTitle property.
        /// Changes to that property's value raise the PropertyChanged event. 
        /// </summary>
        public string WelcomeTitle
        {
            get
            {
                return _welcomeTitle;
            }
            set
            {
                Set(ref _welcomeTitle, value);
            }
        }

        /// <summary>
        /// Initializes a new instance of the MainViewModel class.
        /// </summary>
        public MainViewModel(IDataService dataService)
        {
            _dataService = dataService;
            _dataService.GetData(
                (item, error) =>
                {
                    if (error != null)
                    {
                        // Report error here
                        return;
                    }

                    WelcomeTitle = item.Title;
                });
        }

        ////public override void Cleanup()
        ////{
        ////    // Clean up if needed

        ////    base.Cleanup();
        ////}
    }
}

ViewModelLocator.cs(我也没有更改任何内容。)

/*
  In App.xaml:
  <Application.Resources>
      <vm:ViewModelLocatorTemplate xmlns:vm="clr-namespace:WpfDataBindingUserControlT1.ViewModel"
                                   x:Key="Locator" />
  </Application.Resources>

  In the View:
  DataContext="{Binding Source={StaticResource Locator}, Path=ViewModelName}"
*/

using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Ioc;
using Microsoft.Practices.ServiceLocation;
using WpfDataBindingUserControlT1.Model;

namespace WpfDataBindingUserControlT1.ViewModel
{
    /// <summary>
    /// This class contains static references to all the view models in the
    /// application and provides an entry point for the bindings.
    /// <para>
    /// See http://www.mvvmlight.net
    /// </para>
    /// </summary>
    public class ViewModelLocator
    {
        static ViewModelLocator()
        {
            ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);

            if (ViewModelBase.IsInDesignModeStatic)
            {
                SimpleIoc.Default.Register<IDataService, Design.DesignDataService>();
            }
            else
            {
                SimpleIoc.Default.Register<IDataService, DataService>();
            }

            SimpleIoc.Default.Register<MainViewModel>();
        }

        /// <summary>
        /// Gets the Main property.
        /// </summary>
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance",
            "CA1822:MarkMembersAsStatic",
            Justification = "This non-static member is needed for data binding purposes.")]
        public MainViewModel Main
        {
            get
            {
                return ServiceLocator.Current.GetInstance<MainViewModel>();
            }
        }

        /// <summary>
        /// Cleans up all the resources.
        /// </summary>
        public static void Cleanup()
        {
        }
    }
}

Answer 1

将此行添加到您的 SimpleUserControl.cs构造函数

public SimpleUserControl()
{
    InitializeComponent();

    (this.Content as FrameworkElement).DataContext = this;
}    

您基本上是在设置 DataContext UserControl 中的第一个元素.

Jerry Nixon 对此有一篇很棒的文章 here

更新
忘记添加摆脱 RelativeSource例如

<local:SimpleUserControl CellValue="{Binding WelcomeTitle}" />