I dont understand why OnPropertyChanged is not firing in neither my Model or ViewModel

Question

I am using the MVVM Community Tollkit and below is the generated code. I also included my Model code and the OnPropertyChanged Method. I put a breakpoint in the generated code on the property Spousessn and it was fired and OnPropertyChanged in the generated code is only called if there is a value in spousessn and is called as I change the text in the bound control. but if there is no initial value for spousessn then OnPropertyChanged is never called nor is it called as i change the the text in the bound control. My issue here is why is the method OnPropertyChanged never fired in my Model Code.

namespace ModelLibrary
{
    partial class PYEModel
    {
        /// <inheritdoc cref="spousessn"/>
        [global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", "8.1.0.0")]
        [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
        public string Spousessn
        {
            get => spousessn;
            set
            {
                if (!global::System.Collections.Generic.EqualityComparer<string>.Default.Equals(spousessn, value))
                {
                    OnSpousessnChanging(value);
                      OnPropertyChanging(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangingArgs.Spousessn);
                    spousessn = value;
                    OnSpousessnChanged(value);
                    OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.Spousessn);
                }
            }
        }

public partial class PYEModel:ObservableObject
{
	int ID { get; set; }
	[ObservableProperty]
	public string spousessn;
}

protected void OnPropertyChanged(string? propertyName = default)
{
}

Answer 1

Hello,

If you want to re-write the OnPropertyChanged in the ObservableObject.

This OnPropertyChanged(PropertyChangedEventArgs e) is virtual method, you need to add **override **in it and If you want to fire OnPropertyChanged method when value of property changed, you have to invoke the ObservableObject.OnPropertyChanged method by base.OnPropertyChanged(e);.

You can refer to the following code.

public partial class MyViewModel: ObservableObject
    {
 

        protected override void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            ArgumentNullException.ThrowIfNull(e);
           base.OnPropertyChanged(e);
          
        }
}

Best Regards,

Leon Lu

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