Observable Validator does not work in wpf-CodePudding

I am working in wpf mvvm app, and I also use Community toolkit.mvvm also. Here I implement Observable validator for textboxes but it does not effect on user interface,

ViewModel:

 public partial class UserViewModel :  ObservableValidator
    {
        [ObservableProperty]
        [Required(ErrorMessage ="Name is Required")]
        [MinLength(3)]
        private string name= "";
    }

Xaml:

  <TextBox Text="{Binding Name,UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>

When I type on textbox less than 3 character and leave it It does not effect, The TextBox accept characters in every range and also accept empty.

After Edited: Thank You! Mr. @mm8

I just change my ViewModel property like this, I think I have missed third parameter of SetProperty which is 'true', Now its working. I see the red border while its invalid, But i don't see the error message.

ViewModel:

 public partial class UserViewModel :  ObservableValidator
    {
private string username;
        [Required(ErrorMessage ="Name is Required")]
        [MinLength(3, ErrorMessage ="Name Should be at least 3 character")]
        public string Username
        {
            get => username;
            set => SetProperty(ref username, value, true);
        }
}

Xaml:

 <TextBox Text="{Binding Username, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>

I have add ValidatesOnDataErrors=True, ValidatesOnNotifyDataErrors=True, NotifyOnValidationError=True to xaml but I could not see the error message.

CodePudding user response：

Confirm that the binding is working. Setting the ValidatesOnDataErrors property of the binding to true shouldn't be necessary:

<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged,
    ValidatesOnDataErrors=True}"/>