Today I've tried to find a way how to pass EventArgs as CommandParameter to DelegateCommand triggered by EventTrigger. By reverse engineering of default InvokeCommandAction I find that blend team just ignores event args.
To resolve this issue I have created my own action for triggering delegate commands.
public sealed class InvokeDelegateCommandAction : TriggerAction<DependencyObject>
{
/// <summary>
///
/// </summary>
public static readonly DependencyProperty CommandParameterProperty =
DependencyProperty.Register("CommandParameter", typeof(object), typeof(InvokeDelegateCommandAction), null);
/// <summary>
///
/// </summary>
public static readonly DependencyProperty CommandProperty = DependencyProperty.Register(
"Command", typeof(ICommand), typeof(InvokeDelegateCommandAction), null);
/// <summary>
///
/// </summary>
public static readonly DependencyProperty InvokeParameterProperty = DependencyProperty.Register(
"InvokeParameter", typeof(object), typeof(InvokeDelegateCommandAction), null);
private string commandName;
/// <summary>
///
/// </summary>
public object InvokeParameter
{
get
{
return this.GetValue(InvokeParameterProperty);
}
set
{
this.SetValue(InvokeParameterProperty, value);
}
}
/// <summary>
///
/// </summary>
public ICommand Command
{
get
{
return (ICommand)this.GetValue(CommandProperty);
}
set
{
this.SetValue(CommandProperty, value);
}
}
/// <summary>
///
/// </summary>
public string CommandName
{
get
{
return this.commandName;
}
set
{
if (this.CommandName != value)
{
this.commandName = value;
}
}
}
/// <summary>
///
/// </summary>
public object CommandParameter
{
get
{
return this.GetValue(CommandParameterProperty);
}
set
{
this.SetValue(CommandParameterProperty, value);
}
}
/// <summary>
///
/// </summary>
/// <param name="parameter"></param>
protected override void Invoke(object parameter)
{
this.InvokeParameter = parameter;
if (this.AssociatedObject != null)
{
ICommand command = this.ResolveCommand();
if ((command != null) && command.CanExecute(this.CommandParameter))
{
command.Execute(this.CommandParameter);
}
}
}
private ICommand ResolveCommand()
{
ICommand command = null;
if (this.Command != null)
{
return this.Command;
}
var frameworkElement = this.AssociatedObject as FrameworkElement;
if (frameworkElement != null)
{
object dataContext = frameworkElement.DataContext;
if (dataContext != null)
{
PropertyInfo commandPropertyInfo = dataContext
.GetType()
.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.FirstOrDefault(
p =>
typeof(ICommand).IsAssignableFrom(p.PropertyType) &&
string.Equals(p.Name, this.CommandName, StringComparison.Ordinal)
);
if (commandPropertyInfo != null)
{
command = (ICommand)commandPropertyInfo.GetValue(dataContext, null);
}
}
}
return command;
}
}
Example:
<ComboBox>
<ComboBoxItem Content="Foo option 1" />
<ComboBoxItem Content="Foo option 2" />
<ComboBoxItem Content="Foo option 3" />
<Interactivity:Interaction.Triggers>
<Interactivity:EventTrigger EventName="SelectionChanged" >
<Presentation:InvokeDelegateCommandAction
Command="{Binding SubmitFormCommand}"
CommandParameter="{Binding RelativeSource={RelativeSource Self}, Path=InvokeParameter}" />
</Interactivity:EventTrigger>
</Interactivity:Interaction.Triggers>
</ComboBox>
BTW: InvokeCommanAction CommandName property are trying to find command in properties of view. It very strange, because in MVVM pattern command should be in viewmodel supplied to datacontext.