绑定已加载的事件

本文关键字：事件 加载 绑定 | 更新日期: 2023-09-27 18:12:24

我试图显示一个登录窗口一旦我的主窗口加载，同时坚持MVVM模式。所以我试图将我的主窗口加载事件绑定到我的视图模型中的事件。以下是我尝试过的:

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;
        }
    }
}

我得到的错误信息是"Loaded="{Binding ShowLogInWindow}"是无效的。'{Binding ShowLogInWindow}'不是一个有效的事件处理程序方法名。只有生成的或代码隐藏类上的实例方法才是有效的。"

绑定已加载的事件

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

然后在XAML中添加名称空间:

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

然后你可以这样做:

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

请注意，您将不得不使用ICommand(或DelegateCommand，如果您使用Prism，或RelayCommand，如果您使用MVVMLight)，并且您的窗口的DataContext必须持有iccommand。

使用附加行为。这在MVVM ....是允许的

(下面的代码可能会/可能不会这样编译)

XAML… 

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

代码后面…

  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....
      }
  }

和附加行为…

  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源代码可以在网上找到…它是最适合MVVM的ICommand API。

修正了两个语法错误

更新:

我写了一篇关于方法绑定的一个更灵活的新版本的文章，它在这里使用了稍微不同的语法:

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

完整的代码清单在这里:

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

任何未来的更新都会发布到博客上，所以我建议在那里查看最新版本。

原始答:

。. 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);
}

更多细节可在这里找到:http://www.singulink.com/CodeIndex/post/building-the-ultimate-wpf-event-method-binding-extension

完整的类代码在这里:https://gist.github.com/mikernet/4336eaa8ad71cb0f2e35d65ac8e8e161

在AttachedCommandBehavior V2中提出了一种更通用的使用行为的方法，即ACB，它甚至支持多个事件到命令绑定，

下面是一个非常基本的用法示例:

<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"
/>

对于VS 2013 Update 5，我无法绕过"无法转换类型为'System.Reflection '的对象"。RuntimeEventInfo'类型为'System.Reflection.MethodInfo '。在"Core"目录下，我做了一个简单的接口

interface ILoad
    {
        void load();
    }

我的viewModel已经有load()函数实现了ilload。在我的. example .cs中，我通过ilload调用ViewModel load()。

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

除了POCO加载之外，xaml.cs对ViewModel一无所知，而ViewModel对xaml.cs一无所知。ml_loaded事件被映射到ViewModel load()。

相关文章：