Pass String to method via CommandParameter

Question

I would like to ask, is it possible to pass string value from view (xaml) to property in ViewModel?

I have Two tabs. First is "Process" and the second is "Non-Process". Depends on that string value RelayCommand will execute and fire method with DispatcherTimer (if Process then Dispatcher1, if Non-Process then Dispatcher2).

xaml:

<i:Interaction.Triggers>
    <i:EventTrigger EventName="PreviewMouseDown" >
       <cmd:EventToCommand Command="{Binding EmployeeViewM.MeasurementEndExecution}"/>
    </i:EventTrigger>
</i:Interaction.Triggers>

Can I use CommandParameter and CommandParameterValue to pass that string to the property?

Thank you for any suggestion

Before asking if you can, did you try it? Of course you can use CommandParameter, and it haven't to be a string, it can be anything you want and it can bind to any property you want. If you have 2 windows, in the first you can pass the string "process" and in the second "non-process". The method that the command raises has a parameter of type object, and it is exactly the parameter that the window passes to the VM. — Massimiliano Kraus
What did you try? What happened? How was that different from what you wanted? Please provide a good minimal reproducible example that shows clearly what you're trying to do, along with a precise description of what specific problem you are having getting the code to work. — Peter Duniho

Kylo Ren Kylo Ren · Accepted Answer · 2016-06-01T08:00:30

Yes you can, like below:

<i:Interaction.Triggers>
    <i:EventTrigger EventName="PreviewMouseDown" >
        <cmd:EventToCommand Command="{Binding EmployeeViewM.MeasurementEndExecution}" CommandParameter="Process"/>
    </i:EventTrigger>
</i:Interaction.Triggers>

And/OR

<i:Interaction.Triggers>
    <i:EventTrigger EventName="PreviewMouseDown" >
        <cmd:EventToCommand Command="{Binding EmployeeViewM.MeasurementEndExecution}" CommandParameter="Non-Process"/>
    </i:EventTrigger>
</i:Interaction.Triggers>

Hopefully your RelayCommand (or ICommand implementation) is already accepting CommandParameter. Like below.

 public class RelayCommand : ICommand
{
    #region Fields

    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;

    #endregion // Fields

    #region Constructors

    /// <summary>
    /// Creates a new command that can always execute.
    /// </summary>
    /// <param name="execute">The execution logic.</param>
    public RelayCommand(Action<object> execute)
        : this(execute, null)
    {
    }

    /// <summary>
    /// Creates a new command.
    /// </summary>
    /// <param name="execute">The execution logic.</param>
    /// <param name="canExecute">The execution status logic.</param>
    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");

        _execute = execute;
        _canExecute = canExecute;
    }

    #endregion // Constructors

    #region ICommand Members


    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute(parameter);
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public void Execute(object parameter)
    {
        _execute(parameter);
    }

    #endregion // ICommand Members
}

Pass String to method via CommandParameter

1 Answers