Where should the Command and Command_CanExecute logic of my UserControl reside?-CodePudding

I have a view PeopleView that displays a list of People bound to a collection of People in PeopleViewModel.

In a panel within PeopleView I have a form (just a collection of text boxes and a button) which allows users to add a new person (People).

Initially I had this collection of controls as part of PeopleView but I want to separate it out into a separate UserControl (AddPerson) as it doesn't necessarily depend on the existing list of people and this AddPerson control could exist anywhere else in the application. I might want to reuse it elsewhere.

However, I'm struggling to work out where I should now be putting my button command and the associated CanExecute logic now.

It would have been in the PeopleViewModel but my AddPerson UserControl doesn't have a ViewModel. I've read that typically you wouldn't have a ViewModel for a UserControl, but I don't know how else I can make a reusable control that also contains its own business logic?

Should my AddPerson UserControl have a ViewModel, or should I be doing the business logic in the codebehind (seems very unlikely), or something else?

CodePudding user response：

Commands traditionally go in the ViewModel but there's no hard fast rule on this. If you'd like to make a more reusable control, you can create a command dependency property on the control itself and then bind it to a command in your view model when the control is implemented.

This is identical to how button command is implemented

For example

MyUserControl.Xaml

<UserControl x:name="self">
    <Grid>
       <Button Command="{Binding ElementName=self, Path=MyDPCommand}"/>
    </Grid>
</UserControl>

MyUserControl.Xaml.cs

public ICommand MyDPCommand
{
    get { return (ICommand)GetValue(MyDPCommandProperty); }
    set { SetValue(MyDPCommandProperty, value); }
}

public static readonly DependencyProperty MyDPCommandProperty =
            DependencyProperty.Register(nameof(MyDPCommand), typeof(ICommand), typeof(MyUserControl), new PropertyMetadata(null));

And then in your implementation xaml you can bind it back to your viewmodel

MyView.Xaml

<MyUserControl MyDpCommand="{Binding MyViewModelCommand}"/>

CodePudding user response：

In the end I've gone the route of implementing a ViewModel for my AddPerson view because, although it is technically a UserControl, I really am using it like any other view rather than a generic control.