CODEWITHSUNDEEP
wpfbinding
user2678787
user2678787

Reputation: 149

Bind Control to Two properties

Using MVVM pattern and WPF, I would like to bind my controls to two properties. Let's say I have a label that is bind to property on VM1 and I would like to bind it as well to the property on VM2 to send received value from VM1 to VM2.

I could use messenger and for multiple items Tuple Class, but I was wondering if there is another solution for that. Multibinding? but then I need ValueConverter.

Thank you for any suggestions.

Upvotes: 3

Views: 136

Answers (2)

Bahman_Aries
Bahman_Aries

Reputation: 4808

Since The View-Model is an abstraction of the view that exposes public properties and commands, it doesn't make a lot of sense for a view to have two view-models the way you explained. It'll be more rational if there is a VM class as the view-model of your view that has two properties of type VM1 and VM2. Then the binding would be on VM.VM1.YourText and you can notify VM2 via events like this:

in VM1:

    public event EventHandler<EventArgs> ValueChanged;

    string _yourText;
    public string YourText
    {
        get
        {
            return _yourText;
        }
        set
        {
            _yourText= value;
            if (ValueChanged != null)
                ValueChanged(_yourText, new EventArgs());
        }
    }

In VM:

    public VM1 Vm1 {get; set;}
    public VM2 Vm2 {get; set;}

    public VM()
    {
        InitializeComponent();
        Vm1 = new VM1();
        Vm2 = new VM2();
        Vm1.ValueChanged += Item_ValueChanged;
        DataContext = this;
    }

    void Item_ValueChanged(object sender, EventArgs e)
    {
        VM2.YourAnotherText = sender.ToString();
    }

Upvotes: 1

Michał Turecki
Michał Turecki

Reputation: 3167

If 2 properties are connected, usually INotifyPropertyChanged can be utilized to notify about a change of 2 or more properties if on the same ViewModel.

What I understand is that you want also to notify a View attached to a ViewModel about a change of a property on another ViewModel. This is usually done by letting ViewModels exchange information.

If that's a one rare case, using message bus for that might be an overkill. Usually keeping a reference to each view model and changing properties from outside should be all right. To keep separation of concerns you can create an interface on one or both viewmodels and reference this interface instead of a concrete type.

Overall keeping a single binding between a control and property keeps it simple and easy to understand and you should worry about making sure that this property handles all changes to/from other VMs.

Upvotes: 1

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