Question

我正在尝试在MainWindow加载时显示登录窗口，同时坚持使用MVVM模式。所以我试图将我的主要Windows Loaded事件绑定到我的viewmodel中的事件。这是我尝试过的：

MainWindowView.xaml

 <Window x:Class="ScrumManagementClient.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        DataContext="ViewModel.MainWindowViewModel"
        Loaded="{Binding ShowLogInWindow}">
    <Grid>

    </Grid>
 </Window>

MainWindowViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ScrumManagementClient.ViewModel
{
    class MainWindowViewModel : ViewModelBase
    {
        public void ShowLogInWindow(object sender, EventArgs e)
        {
            int i = 0;
        }
    }
}

我得到的错误消息是“Loaded =”{Binding ShowLogInWindow}“无效。”{Binding ShowLogInWindow}'不是有效的事件处理程序方法名称。只有生成的或代码隐藏类的实例方法是有效的“。

Answer 1

您将不得不使用System.Windows.Interactivity dll。

然后在XAML中添加命名空间：

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

然后你可以做类似的事情：

<i:Interaction.Triggers>
    <i:EventTrigger EventName="Loaded">
        <i:InvokeCommandAction Command="{Binding MyICommandThatShouldHandleLoaded}" />
    </i:EventTrigger>
</i:Interaction.Triggers>

请注意，您必须使用ICommand（或者，如果使用MVVMLight，则使用DelegateCommand或RelayCommand），并且Window的DataContext必须包含该ICommand。

Answer 2

使用附加行为。这在MVVM中是允许的....

（下面的代码可能/可能不会像那样编译）

XAML ......

   <Window x:Class="..."
           ...
           xmlns:local="... namespace of the attached behavior class ..."
           local:MyAttachedBehaviors.LoadedCommand="{Binding ShowLogInWindowCommand}">
     <Grid>
     </Grid>
  </Window>

代码背后......

  class MainWindowViewModel : ViewModelBase
  {
      private ICommand _showLogInWindowCommand;

      public ICommand ShowLogInWindowCommand
      {
         get
         {
              if (_showLogInWindowCommand == null)
              {
                  _showLogInWindowCommand = new DelegateCommand(OnLoaded)
              }
              return _showLogInWindowCommand;
         }
      }

      private void OnLoaded()
      {
          //// Put all your code here....
      }
  }

附加行为......

  public static class MyAttachedBehaviors
  {
      public static DependencyProperty LoadedCommandProperty
        = DependencyProperty.RegisterAttached(
             "LoadedCommand",
             typeof(ICommand),
             typeof(MyAttachedBehaviors),
             new PropertyMetadata(null, OnLoadedCommandChanged));

      private static void OnLoadedCommandChanged
           (DependencyObject depObj, DependencyPropertyChangedEventArgs e)
      {
          var frameworkElement = depObj as FrameworkElement;
          if (frameworkElement != null && e.NewValue is ICommand)
          {
               frameworkElement.Loaded 
                 += (o, args) =>
                    {
                        (e.NewValue as ICommand).Execute(null);
                    };
          }
      }

      public static ICommand GetLoadedCommand(DependencyObject depObj)
      {
         return (ICommand)depObj.GetValue(LoadedCommandProperty);
      }

      public static void SetLoadedCommand(
          DependencyObject depObj,
          ICommand  value)
      {
         depObj.SetValue(LoadedCommandProperty, value);
      }
  }

DelegateCommand源代码可以在互联网上找到...它是最适合MVVM的ICommand API。

编辑：19.07.2016修复了两个小的语法错误

Answer 3

<强>更新

我发了一篇关于方法绑定的更灵活版本的帖子，这里使用了稍微不同的语法：

http://www.singulink.com/CodeIndex/post/updated-ultimate-wpf-event-method-binding

完整的代码清单可在此处获取：

https://gist.github.com/mikernet/7eb18408ffbcc149f1d9b89d9483fc19

任何未来的更新都会发布到博客上，因此我建议您查看最新版本。

原始答案：

.NET 4.5+现在支持事件的标记扩展。我用它来创建一个方法绑定，可以像这样使用：

<!--  Basic usage  -->
<Button Click="{data:MethodBinding OpenFromFile}" Content="Open" />

<!--  Pass in a binding as a method argument  -->
<Button Click="{data:MethodBinding Save, {Binding CurrentItem}}" Content="Save" />

<!--  Another example of a binding, but this time to a property on another element  -->
<ComboBox x:Name="ExistingItems" ItemsSource="{Binding ExistingItems}" />
<Button Click="{data:MethodBinding Edit, {Binding SelectedItem, ElementName=ExistingItems}}" />

<!--  Pass in a hard-coded method argument, XAML string automatically converted to the proper type  -->
<ToggleButton Checked="{data:MethodBinding SetWebServiceState, True}"
                Content="Web Service"
                Unchecked="{data:MethodBinding SetWebServiceState, False}" />

<!--  Pass in sender, and match method signature automatically -->
<Canvas PreviewMouseDown="{data:MethodBinding SetCurrentElement, {data:EventSender}, ThrowOnMethodMissing=False}">
    <controls:DesignerElementTypeA />
    <controls:DesignerElementTypeB />
    <controls:DesignerElementTypeC />
</Canvas>

    <!--  Pass in EventArgs  -->
<Canvas MouseDown="{data:MethodBinding StartDrawing, {data:EventArgs}}"
        MouseMove="{data:MethodBinding AddDrawingPoint, {data:EventArgs}}"
        MouseUp="{data:MethodBinding EndDrawing, {data:EventArgs}}" />

<!-- Support binding to methods further in a property path -->
<Button Content="SaveDocument" Click="{data:MethodBinding CurrentDocument.DocumentService.Save, {Binding CurrentDocument}}" />

查看模型方法签名：

public void OpenFromFile();
public void Save(DocumentModel model);
public void Edit(DocumentModel model);

public void SetWebServiceState(bool state);

public void SetCurrentElement(DesignerElementTypeA element);
public void SetCurrentElement(DesignerElementTypeB element);
public void SetCurrentElement(DesignerElementTypeC element);

public void StartDrawing(MouseEventArgs e);
public void AddDrawingPoint(MouseEventArgs e);
public void EndDrawing(MouseEventArgs e);

public class Document
{
    // Fetches the document service for handling this document
    public DocumentService DocumentService { get; }
}

public class DocumentService
{
    public void Save(Document document);
}

可在此处找到更多详细信息：http://www.singulink.com/CodeIndex/post/building-the-ultimate-wpf-event-method-binding-extension

完整的课程代码可在此处获得： https://gist.github.com/mikernet/4336eaa8ad71cb0f2e35d65ac8e8e161

Answer 4

在AttachedCommandBehavior V2 aka ACB提出了一种使用行为的更通用的方法，它甚至支持多个事件到命令的绑定，

这是一个非常基本的使用示例：

<Window x:Class="Example.YourWindow"
        xmlns:local="clr-namespace:AttachedCommandBehavior;assembly=AttachedCommandBehavior"
        local:CommandBehavior.Event="Loaded"
        local:CommandBehavior.Command="{Binding DoSomethingWhenWindowIsLoaded}"
        local:CommandBehavior.CommandParameter="Some information"
/>

Answer 5

对于VS 2013 Update 5，我无法绕过＆＃34;无法转换类型＆System; System.Reflection.RuntimeEventInfo＆＃39;键入＆＃39; System.Reflection.MethodInfo＆＃34;。取而代之的是＆＃34; Core＆＃34;目录我做了一个简单的界面

interface ILoad
    {
        void load();
    }

我的viewModel已经有了实现ILoad的load（）函数。在我的.xaml.cs中，我通过ILoad调用ViewModel load（）。

private void ml_Loaded(object sender, RoutedEventArgs e)
{
    (this.ml.DataContext as Core.ILoad).load();
}

除了POCO ILoad之外，xaml.cs对ViewModel一无所知，ViewModel对xaml.cs一无所知。 ml_loaded事件映射到ViewModel load（）。

绑定Loaded事件？

5 个答案: