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在上一節(jié)中我介紹了“MVVM中輕松實(shí)現(xiàn)Command綁定（四）獲取事件參數(shù)EventArgs”，通過Loaded事件傳遞控件對象，然后添加事件方法，這樣做是可以的，但是不符合MVVM的思想，今日我介紹另一種方法，通過擴(kuò)展interactivity的InvokeCommandAction來實(shí)現(xiàn)事件參數(shù)傳遞。 先來看普通的InvokeCommandAction方式
<Window x:Class="EventArgsInViewModel.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:loc="clr-namespace:EventArgsInViewModel"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<loc:MainWindowViewModel />
</Window.DataContext>
<Grid>
<Button Content="Button" Height="38" HorizontalAlignment="Left" Margin="50,52,0,0" Name="button1" VerticalAlignment="Top" Width="138">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<i:InvokeCommandAction
Command="{Binding ClickCommand}" CommandParameter="{Binding ElementName=button1}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
</Grid>
</Window>
現(xiàn)在為了擴(kuò)展CommandParameter，定義ExCommandParameter類
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
namespace EventArgsInViewModel {
/// <summary>
/// 擴(kuò)展CommandParameter，使CommandParameter可以帶事件參數(shù)
/// </summary>
public class ExCommandParameter {
/// <summary>
/// 事件觸發(fā)源
/// </summary>
public DependencyObject Sender { get; set; }
/// <summary>
/// 事件參數(shù)
/// </summary>
public EventArgs EventArgs { get; set; }
/// <summary>
/// 額外參數(shù)
/// </summary>
public object Parameter { get; set; }
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Interactivity;
using System.Windows.Input;
using System.Reflection;
namespace EventArgsInViewModel {
/// <summary>
/// 擴(kuò)展的InvokeCommandAction
/// </summary>
public class ExInvokeCommandAction : TriggerAction<DependencyObject> {
private string commandName;
public static readonly DependencyProperty CommandProperty = DependencyProperty.Register("Command", typeof(ICommand), typeof(ExInvokeCommandAction), null);
public static readonly DependencyProperty CommandParameterProperty = DependencyProperty.Register("CommandParameter", typeof(object), typeof(ExInvokeCommandAction), null);
/// <summary>
/// 獲得或設(shè)置此操作應(yīng)調(diào)用的命令的名稱。
/// </summary>
/// <value>此操作應(yīng)調(diào)用的命令的名稱。</value>
/// <remarks>如果設(shè)置了此屬性和 Command 屬性，則此屬性將被后者所取代。</remarks>
public string CommandName {
get {
base.ReadPreamble();
return this.commandName;
}
set {
if (this.CommandName != value) {
base.WritePreamble();
this.commandName = value;
base.WritePostscript();
}
}
}
/// <summary>
/// 獲取或設(shè)置此操作應(yīng)調(diào)用的命令。這是依賴屬性。
/// </summary>
/// <value>要執(zhí)行的命令。</value>
/// <remarks>如果設(shè)置了此屬性和 CommandName 屬性，則此屬性將優(yōu)先于后者。</remarks>
public ICommand Command {
get {
return (ICommand)base.GetValue(ExInvokeCommandAction.CommandProperty);
}
set {
base.SetValue(ExInvokeCommandAction.CommandProperty, value);
}
}
/// <summary>
/// 獲得或設(shè)置命令參數(shù)。這是依賴屬性。
/// </summary>
/// <value>命令參數(shù)。</value>
/// <remarks>這是傳遞給 ICommand.CanExecute 和 ICommand.Execute 的值。</remarks>
public object CommandParameter {
get {
return base.GetValue(ExInvokeCommandAction.CommandParameterProperty);
}
set {
base.SetValue(ExInvokeCommandAction.CommandParameterProperty, value);
}
}
/// <summary>
/// 調(diào)用操作。
/// </summary>
/// <param name="parameter">操作的參數(shù)。如果操作不需要參數(shù)，則可以將參數(shù)設(shè)置為空引用。</param>
protected override void Invoke(object parameter) {
if (base.AssociatedObject != null) {
ICommand command = this.ResolveCommand();
/*
* ★★★★★★★★★★★★★★★★★★★★★★★★
* 注意這里添加了事件觸發(fā)源和事件參數(shù)
* ★★★★★★★★★★★★★★★★★★★★★★★★
*/
ExCommandParameter exParameter = new ExCommandParameter {
Sender=base.AssociatedObject,
Parameter = GetValue(CommandParameterProperty),
EventArgs=parameter as EventArgs
};
if (command != null && command.CanExecute(exParameter)) {
/*
* ★★★★★★★★★★★★★★★★★★★★★★★★
* 注意將擴(kuò)展的參數(shù)傳遞到Execute方法中
* ★★★★★★★★★★★★★★★★★★★★★★★★
*/
command.Execute(exParameter);
}
}
}
private ICommand ResolveCommand() {
ICommand result = null;
if (this.Command != null) {
result = this.Command;
} else {
if (base.AssociatedObject != null) {
Type type = base.AssociatedObject.GetType();
PropertyInfo[] properties = type.GetProperties(BindingFlags.Instance | BindingFlags.Public);
PropertyInfo[] array = properties;
for (int i = 0; i < array.Length; i++) {
PropertyInfo propertyInfo = array[i];
if (typeof(ICommand).IsAssignableFrom(propertyInfo.PropertyType) && string.Equals(propertyInfo.Name, this.CommandName, StringComparison.Ordinal)) {
result = (ICommand)propertyInfo.GetValue(base.AssociatedObject, null);
}
}
}
}
return result;
}
}
}
<Window x:Class="EventArgsInViewModel.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:loc="clr-namespace:EventArgsInViewModel"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<loc:MainWindowViewModel />
</Window.DataContext>
<Grid>
<Button Content="Button" Height="38" HorizontalAlignment="Left" Margin="50,52,0,0" Name="button1" VerticalAlignment="Top" Width="138">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<!--★★★擴(kuò)展的InvokeCommandAction★★★-->
<loc:ExInvokeCommandAction
Command="{Binding ClickCommand}" CommandParameter="{Binding ElementName=button1}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
</Grid>
</Window>
ViewModel代碼
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;
using Microsoft.Practices.Prism.Commands;
using System.Windows;
namespace EventArgsInViewModel {
public class MainWindowViewModel {
public ICommand ClickCommand {
get {
return new DelegateCommand<ExCommandParameter>((p) => {
RoutedEventArgs args = p.EventArgs as RoutedEventArgs;
MessageBox.Show(args.ToString());
},
(p) => {
return true;
}
);
}
}
}
}
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