MVVM Light View not refreshing binding property

Question

I use MVVM Light. My Model inherits from MVVM Light's ObservableObject. The Model has a property X

    public float X
    {
        get
        {
            return x_;
        }
        set
        {
            Set<float>(() => this.X, ref x_, value);
        }
    }

In my ViewModel I have a property X

        public float X
        {
            get
            {
                myModel.X;
            }
        }

My View has a label where the content is binding to the ViewModel property X.

(DataContext is set to ViewModel)

When the value of property X in Model is updated from code, the label in the view never gets updated.

Question what is the recommended way to make sure that the View correctly reflects the updated value?

(If I make a property in my ViewModel that returns the Model, I could bind direclty to Model.X in my View. But I want my View to bind to the ViewModel not directly down to the Model)

When myModel.X fires its PropertyChanged event, that does not automatically fire the ViewModel's PropertyChanged event. Make MyModel a public property in the ViewModel and bind to MyModel.X. — Clemens
Okay so that is the correct to solve it after all. I have to make the complete model available for the View to bind to, I had hoped there was a way to restrict the bindings to the ViewModel class only. — Johan
If there is no better way please feel free to post your comment as an answer and I will set it to the answer unless I get a better solution. — Johan

Clemens Clemens · Accepted Answer · 2018-08-10T16:54:12

When myModel.X fires the PropertyChanged event, that does not automatically fire the ViewModel's PropertyChanged.

Moreover, if your Model class already implements INotifyPropertyChanged, there is no need to duplicate the X property in the ViewModel class.

Just turn the myModel member into a public property

public class ViewModel
{
     public Model MyModel { get; set; } 
}

and bind to it by {Binding MyModel.X}.

MVVM Light View not refreshing binding property

1 Answers