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c#wpfmvvmmodelviewmodel

How do I get WPF Databinding to notice changes to properties on the model?

I've created an WPF MVVM app. The ViewModel has properties I can bind to from the View. But one of the properties is basically a model for a json document that has many properties which are either int, string or some other model and so on. In my view I have controls that update these properties. The object updates but no PropertyChanged events fire.

What's a clean way to handle a situation like this? Do I have to create dozens of property accessors in my ViewModel or is there a better way?

Edit for more detail:

Now using Fody per Andy:

In my VM:

public AppModel AppModel { get; set; }

In my Models

public class AppModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    public string ApplicationName { get; set; }
    public string ApplicationVersion { get; set; }
}

In my View:

<TextBox Text="{Binding AppModel.ApplicationName, Mode=TwoWay }"/>
<TextBox Text="{Binding AppModel.ApplicationVersion, Mode=TwoWay}"/>

When I start the app and create a new doc I show null in the textbox and the json view.

New Doc

Then I update the textboxes (changing selection a could times to be sure it updated) but nothing fires to call my code to repopulate the JSON text

After entering data

I click the Save button which has code to serialize the object to JSON and I can see my data does exist in the object.

After clicking Save

Solution

  • Since you want to stay MVVM and not add a bunch of properties (which makes sense,since the JSON schema could change). I would use data templates.

    I would build a hierarchical collection of 'PropertyVMs' from the JSON that is bound to the ItemSource of a TreeView. Then define a DataTemplate for the view of a single PropertyVM. That template would display the name of the node and the node content. When the content of a node changes, that node can propagate that notification back wherever it needs to go so that the underlying JSON gets updated.

    This gives you a lot of flexibility. You could even define different data templates for different kinds of properties, like a numeric up down for numbers and a date time picker for DateTime.