Update UI on Value Change from ViewModel

Question

I'm having a problem getting my UI to update from the ViewModel. Basically, I have a text entry that takes in a zip code. Upon change of that Property, I call the USPSService to get the city and state and fill in those Properties programmatically, which it does, but the UI never updates. I have a 'main' View Model, that has a property of another class that has the fields.

public partial class AddCustomerViewModel : ObservableObject
{
    USPSService _uspsService;
    public AddCustomerViewModel(USPSService uspsService)
    {
        DataFormObject = new AddCustomerDataFormObject();
        DataFormObject.PropertyChanged += DataFormObject_PropertyChanged;
        Title = "Customer Information";
        CurrentLocation = ApplicationState.DefaultLocation;
        _uspsService = uspsService;
    }

    private async void DataFormObject_PropertyChanged(object? sender, PropertyChangedEventArgs e)
    {
        var dataObject = sender as AddCustomerDataFormObject;
        var propertyName = e.PropertyName;
        if (propertyName == "ZipCode")
        {
            await GetZipCodeInformation();
        }
    }

    public AddCustomerViewModel() { }

    public AddCustomerDataFormObject DataFormObject { get; set; }

    public async Task GetZipCodeInformation()
    {
        string zipCode = DataFormObject.ZipCode;
        if (zipCode.Length == 5)
        {
            var info = await _uspsService.GetZipCodeInformation(zipCode);
            if (info != null)
            {
                DataFormObject.City = info.city;
                DataFormObject.State = info.state;                    
            }
        }
    }    
}

public class AddCustomerDataFormObject : ObservableObject
{

    public AddCustomerDataFormObject() {}

    string addressLine1 = string.Empty;
    string addressLine2 = string.Empty;
    string city = string.Empty;
    string state = string.Empty;
    string zipCode = string.Empty;

   
    public string AddressLine1 { get { return addressLine1; } set { addressLine1 = value; } }
    public string AddressLine2 { get { return addressLine2; } set { addressLine2 = value; } }
    public string City 
    { 
        get { return city; } 
        set { 
            if (city != value)
            {
                SetProperty(ref city, value);
            }
        } 
    }
    public string State 
    { 
        get { return state; } 
        set { 
            if (state != value)
            {
                SetProperty(ref state, value);
            }
        } 
    }

    [RegularExpression(pattern: "^(\d{5})?$", ErrorMessage = "Invalid Zip Code")]
    public string ZipCode 
    { 
        get { return zipCode; } 
        set {
            if (zipCode != value)
            {
                SetProperty(ref zipCode, value);
            }
        } 
    }
}

I have the AddCustomerViewModel as the BindingContext for the view, and then the AddCustomerDataFormObject as the Binding object to the DataForm (Syncfusion). This won't work with Entries or Labels either, so not thinking its Syncfusion.

Here's the 'code behind' of my XAML page:

public partial class AddCustomerMain : ContentPage
{
    AddCustomerViewModel _viewModel;
    public AddCustomerMain(AddCustomerViewModel viewModel)
    {
        InitializeComponent();
        BindingContext = viewModel;
        _viewModel = viewModel;
        _viewModel.DataFormObject.PropertyChanged += DataFormObject_PropertyChanged;
    }

    private async void DataFormObject_PropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        var dataItem = sender as AddCustomerDataFormObject;
        if (e.PropertyName == "State")
        {
            this.StateDataFormTextItem.LabelText = dataItem.State;
        }    
    }
}

Thoughts? I've tried running the portion of setting the Label Text on the MainThread, but that didn't make a difference. If I look at the properties during debugging, they are all being updated, but the UI isn't showing any changes.

UPDATE: Here's the XAML

Update UI on Value Change from ViewModel

Answers (1)

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