CODEWITHSUNDEEP
c#wpfxamlmvvmbinding
DriLLFreAK100
DriLLFreAK100

Reputation: 1606

WPF - Binding and Command on two different ViewModel

it goes like this.. I have two viewModels under one same XAML file.

ViewModel(1) - Contains a button that has a command that will fire a function inside that view model.

ViewModel(2) - Contains a property that are binded to the XAML

Question: Is it possible for me to update that particular property in ViewModel(2) using the command in ViewModel(1)? If yes, can I have a brief guideline on how to approach it?

The requirement sets me not to make any changes like shifting the property to be in the same viewModel as the command.

Thank you in advance for any help guys :)

Upvotes: 0

Views: 1694

Answers (3)

Sébastien Pertus
Sébastien Pertus

Reputation: 715

I think you should use a Messenger.
Here is a good article about Messenger in mvvm architecture.
A little bit old, but it could help you imo : https://msdn.microsoft.com/en-us/magazine/jj694937.aspx

Here is an example, for you. For instance, I use MVVM Light from Galasoft, to be the most straightforward as possible :) http://www.galasoft.ch/mvvm/

First of all, I recommand you to create an Entity related to your message you want to broadcast :
I have added a simple string property, but obviously you can add whatever you want :)

public class Vm1toVm2Message
{
    public String Message { get; set; }
}

Then in your VM1 you create your message and broadcast it :

public class ViewModel1 : ViewModelBase
{
    private RelayCommand _refreshCommand;
    public RelayCommand RefreshCommand
    {
        get
        {
            return _refreshCommand ?? (_refreshCommand = new RelayCommand(() =>
            {
                // You button command code
                // -------------------

                // Send a message
                Messenger.Default.Send<Vm1toVm2Message>( new Vm1toVm2Message { Message = "Update from VM1" });
            }));
        }
    }
}

And finally in your VM2, you wait for an incoming message :)

public class ViewModel2 : ViewModelBase
{
    public ViewModel2()
    {
        Messenger.Default.Register<Vm1toVm2Message>(this, HandleVm1toVm2Message);
    }

    private void HandleVm1toVm2Message(Vm1toVm2Message msg)
    {
        // Do what you want here
    }
}

Upvotes: 3

Sebastian Siemens
Sebastian Siemens

Reputation: 2421

In viewmodel 1 you can store an action which updates the property in viewmodel 2. In viewmodel 1 you cann invoke the action and viewmodel 2 is changed.

public class SomeOtherClass
{
    public void main()
    {
        var vm1 = new ViewModel1();
        var vm2 = new ViewModel2();

        vm1.ChangeValueAction = new Action(() => { vm2.SomeProperty = String.Empty; });
    }
}

public class ViewModel1
{
    public Action ChangeValueAction { get; set; }

    public void SomeMethod()
    {
        ChangeValueAction.Invoke();
    }
}

public class ViewModel2
{
    public string SomeProperty { get; set; }
}

Upvotes: 1

Amine
Amine

Reputation: 1346

You can try this :

public class FirstViewModel : INotifyPropertyChanged
{
    public delegate void PropertyChangedHandler(object obj);
    public static event PropertyChangedHandler MyPropertyChanged = delegate { };
    public FirstViewModel()
    {
        //Example: here I fire the function in the second ViewModel with parameter
        var obj = new { Name = "Jhon" };
        MyPropertyChanged(obj);
    }
}

Second ViewModel

public class SecondViewModel : INotifyPropertyChanged
{
    public SecondViewModel()
    {
        FirstViewModel.MyPropertyChanged += OnMyPropertyChanged;
    }

    public void OnMyPropertyChanged(object obj)
    {
        //...
    }

    //....
}

Upvotes: 1

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