可以實現鼠標事件綁定到DelegateCommand的功能，對prism中的InvokeCommandAction進行改寫，得到InvokeMouseCommandAction類。
該類使用很簡單，就是 <local:InvokeMouseCommandAction Command="{Binding MouseDownCommand}"/>，在xaml中的詳細語句如下：
<Canvas Width="300" Height="300" Background="AliceBlue">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDown">
<local:InvokeMouseCommandAction Command="{Binding MouseDownCommand}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</Canvas>
在ViewModel中定時DelegateCommand<object>類型對象，不要定義爲DelegateCommand<Point>類型，否則會報
“T for DelegateCommand<T> is not an object nor Nullable”錯誤，即T不是object或nullable類型的錯誤。
public MainWindowViewModel()
{
MouseDownCommand = new DelegateCommand<object>(mHandler);
}
public DelegateCommand<object> MouseDownCommand { get; private set; }
private void mHandler(object o)
{
//if(o is Point p)
// MessageBox.Show(p.ToString());
}
如果要對多種鼠標事件進行命令綁定，則xaml中使用方法如下：
<Canvas Width="300" Height="300" Background="AliceBlue">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDown">
<local:InvokeMouseCommandAction Command="{Binding MouseDownCommand}"/>
</i:EventTrigger>
<i:EventTrigger EventName="MouseMove">
<local:InvokeMouseCommandAction Command="{Binding MouseMoveCommand}"/>
</i:EventTrigger>
<i:EventTrigger EventName="MouseUp">
<local:InvokeMouseCommandAction Command="{Binding MouseUpCommand}"/>
</i:EventTrigger>
<i:EventTrigger EventName="MouseLeave">
<local:InvokeMouseCommandAction Command="{Binding MouseLeaveCommand}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</Canvas>
下面是完整的InvokeMouseCommandAction代碼。該代碼通過修改prism:InvokeCommandParameter類的Invoke方法而得到。
public class InvokeMouseCommandAction:TriggerAction<UIElement>
{
private ExecutableCommandBehavior _commandBehavior;
/// <summary>
/// Dependency property identifying if the associated element should automaticlaly be enabled or disabled based on the result of the Command's CanExecute
/// </summary>
public static readonly DependencyProperty AutoEnableProperty =
DependencyProperty.Register("AutoEnable", typeof(bool), typeof(InvokeMouseCommandAction),
new PropertyMetadata(true, (d, e) => ((InvokeMouseCommandAction)d).OnAllowDisableChanged((bool)e.NewValue)));
/// <summary>
/// Gets or sets whther or not the associated element will automatically be enabled or disabled based on the result of the commands CanExecute
/// </summary>
public bool AutoEnable
{
get { return (bool)GetValue(AutoEnableProperty); }
set { SetValue(AutoEnableProperty, value); }
}
private void OnAllowDisableChanged(bool newValue)
{
var behavior = GetOrCreateBehavior();
if (behavior != null)
behavior.AutoEnable = newValue;
}
/// <summary>
/// Dependency property identifying the command to execute when invoked.
/// </summary>
public static readonly DependencyProperty CommandProperty =
DependencyProperty.Register("Command", typeof(ICommand), typeof(InvokeMouseCommandAction),
new PropertyMetadata(null, (d, e) => ((InvokeMouseCommandAction)d).OnCommandChanged((ICommand)e.NewValue)));
/// <summary>
/// Gets or sets the command to execute when invoked.
/// </summary>
public ICommand Command
{
get { return GetValue(CommandProperty) as ICommand; }
set { SetValue(CommandProperty, value); }
}
private void OnCommandChanged(ICommand newValue)
{
var behavior = GetOrCreateBehavior();
if (behavior != null)
behavior.Command = newValue;
}
/// <summary>
/// Dependency property identifying the command parameter to supply on command execution.
/// </summary>
public static readonly DependencyProperty CommandParameterProperty =
DependencyProperty.Register("CommandParameter", typeof(object), typeof(InvokeMouseCommandAction),
new PropertyMetadata(null, (d, e) => ((InvokeMouseCommandAction)d).OnCommandParameterChanged(e.NewValue)));
/// <summary>
/// Gets or sets the command parameter to supply on command execution.
/// </summary>
public object CommandParameter
{
get { return GetValue(CommandParameterProperty); }
set { SetValue(CommandParameterProperty, value); }
}
private void OnCommandParameterChanged(object newValue)
{
var behavior = GetOrCreateBehavior();
if (behavior != null)
behavior.CommandParameter = newValue;
}
/// <summary>
/// Dependency property identifying the TriggerParameterPath to be parsed to identify the child property of the trigger parameter to be used as the command parameter.
/// </summary>
public static readonly DependencyProperty TriggerParameterPathProperty =
DependencyProperty.Register("TriggerParameterPath", typeof(string), typeof(InvokeMouseCommandAction),
new PropertyMetadata(null, (d, e) => { }));
/// <summary>
/// Gets or sets the TriggerParameterPath value.
/// </summary>
public string TriggerParameterPath
{
get { return GetValue(TriggerParameterPathProperty) as string; }
set { SetValue(TriggerParameterPathProperty, value); }
}
/// <summary>
/// Public wrapper of the Invoke method.
/// </summary>
public void InvokeAction(object parameter)
{
Invoke(parameter);
}
/// <summary>
/// Executes the command
/// </summary>
/// <param name="parameter">This parameter is passed to the command; the CommandParameter specified in the CommandParameterProperty is used for command invocation if not null.</param>
protected override void Invoke(object parameter)
{
//判斷是否對TriggerParameterPath進行了賦值，如果賦值則拋出異常
if (!string.IsNullOrEmpty(TriggerParameterPath))
{
throw new ArgumentOutOfRangeException("TriggerParameterPath should not be assigned any value");
}
//判斷傳入的parameter是否爲 MouseEventArgs類型，如果佈置，則拋出異常。如果是，則計算得到鼠標點座標（相對於出發時間的UI對象），然後點座標傳入命令中
if(parameter is MouseEventArgs mArgs)
{
Point p = mArgs.GetPosition((IInputElement)mArgs.Source);
var behavior = GetOrCreateBehavior();
if (behavior != null)
{
behavior.ExecuteCommand(p);
}
}
else
{
throw new InvalidOperationException("The Trigger event is not mouse relevant");
}
}
/// <summary>
/// Sets the Command and CommandParameter properties to null.
/// </summary>
protected override void OnDetaching()
{
base.OnDetaching();
Command = null;
CommandParameter = null;
_commandBehavior = null;
}
/// <summary>
/// This method is called after the behavior is attached.
/// It updates the command behavior's Command and CommandParameter properties if necessary.
/// </summary>
protected override void OnAttached()
{
base.OnAttached();
// In case this action is attached to a target object after the Command and/or CommandParameter properties are set,
// the command behavior would be created without a value for these properties.
// To cover this scenario, the Command and CommandParameter properties of the behavior are updated here.
var behavior = GetOrCreateBehavior();
behavior.AutoEnable = AutoEnable;
if (behavior.Command != Command)
behavior.Command = Command;
if (behavior.CommandParameter != CommandParameter)
behavior.CommandParameter = CommandParameter;
}
private ExecutableCommandBehavior GetOrCreateBehavior()
{
// In case this method is called prior to this action being attached,
// the CommandBehavior would always keep a null target object (which isn't changeable afterwards).
// Therefore, in that case the behavior shouldn't be created and this method should return null.
if (_commandBehavior == null && AssociatedObject != null)
{
_commandBehavior = new ExecutableCommandBehavior(AssociatedObject);
}
return _commandBehavior;
}
/// <summary>
/// A CommandBehavior that exposes a public ExecuteCommand method. It provides the functionality to invoke commands and update Enabled state of the target control.
/// It is not possible to make the <see cref="InvokeCommandAction"/> inherit from <see cref="CommandBehaviorBase{T}"/>, since the <see cref="InvokeCommandAction"/>
/// must already inherit from <see cref="TriggerAction{T}"/>, so we chose to follow the aggregation approach.
/// </summary>
private class ExecutableCommandBehavior : CommandBehaviorBase<UIElement>
{
/// <summary>
/// Constructor specifying the target object.
/// </summary>
/// <param name="target">The target object the behavior is attached to.</param>
public ExecutableCommandBehavior(UIElement target)
: base(target)
{
}
/// <summary>
/// Executes the command, if it's set.
/// </summary>
public new void ExecuteCommand(object parameter)
{
base.ExecuteCommand(parameter);
}
}
}