Accessing the Command and CommandParameter properties of buttons within a user control - wpf

Question

I have a simple user control that I'm building (something akin to the illustrations below) which is essentially a user control containing a number of buttons.
The main control itself does not have a command or command parameter property, but the four buttons inside it do and I wish to be able to access those from the view model of whatever views I happen to place this control on.
Put simply what is the best way to do this. I simply want to know which button was clicked. Each button is named (so that would I presume take care of the identification side).
Thanks for any suggestions you might have.

Answer 1

If I understood you correctly, you want to get a method called within your viewmodel when one of those 4 buttons is clicked.
A simplified view on the general relationship between viewmodel and view could help. From a view perspective the viewmodel is typically accessed via the datacontext property, i.e. the datacontext propery contains the viewmodel object.
Therefore, set the datacontext in xaml or code behind of your main user control to the viewmodel object that you want to use and bind from the buttons command propeties to the appropriate ICommand properties on the viewmodel that you set before.
namespace UserControlTest
{
/// <summary>
/// Interaktionslogik für MainUserControl.xaml
/// </summary>
public partial class MainUserControl : UserControl
{
public MainUserControl()
{
InitializeComponent();
DataContext = new ViewModel();
}
}
public class ViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public ViewModel()
{
Command = new RelayCommand((obj) => Debug.Print("done"));
}
private ICommand _command;
public ICommand Command
{
get
{
return _command;
}
set
{
_command = value;
RaisePropertyChanged("Command");
}
}
public void RaisePropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public class RelayCommand : ICommand
{
#region Fields
readonly Action<object> _execute;
readonly Predicate<object> _canExecute;
#endregion // Fields
#region Constructors
public RelayCommand(Action<object> execute) : this(execute, null) { }
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
}
}
<UserControl x:Class="UserControlTest.MainUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<Grid>
<StackPanel>
<Button Height="50" Command="{Binding Command}"></Button>
</StackPanel>
</Grid>
</UserControl>