WPF Validation and TextBox Style Management

Question

I created my own custom authentication system for WPF using attribute-based authentication. I am stuck in the last step to highlight a TextBox. In fact, it selects text fields, but all text fields depend on a single HasError property.

public class RegistrationViewModel  : ViewModel
    {
        [NotNullOrEmpty("FirstName should not be null or empty")] 
        public string FirstName { get; set; }

        [NotNullOrEmpty("Middle Name is required!")]
        public string MiddleName { get; set; } 

        [NotNullOrEmpty("LastName should not be null or empty")] 
        public string LastName { get; set; }

        public bool HasError
        {
            get
            {
                **return Errors.Count > 0; // THIS IS THE PROBLEM** 
            }
        }

    }

And here is the XAML code:

 <Style x:Key="textBoxStyle" TargetType="{x:Type TextBox}">                   

            <Style.Triggers>

                <DataTrigger Binding="{Binding Path=HasError}" Value="True">
                    <Setter Property="Background" Value="Red" />
                </DataTrigger>

            </Style.Triggers>

        </Style>

The problem with the above code is that it will highlight all text fields that use "textBoxStyle", even if they are valid. This is because HasError does not check based on an individual property, but as a whole.

Any ideas?

UPDATE 1:

ViewModel contains a collection of errors:

 public class ViewModel : ContentControl, INotifyPropertyChanged
    {
        public static DependencyProperty ErrorsProperty; 

        static ViewModel()
        {
            ErrorsProperty = DependencyProperty.Register("Errors", typeof(ObservableCollection<BrokenRule>), typeof(ViewModel)); 
        }

        public ObservableCollection<BrokenRule> Errors
        {
            get { return (ObservableCollection<BrokenRule>)GetValue(ErrorsProperty); }
            set 
            { 
                SetValue(ErrorsProperty,value);
                OnPropertyChanged("HasError");
             }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected void OnPropertyChanged(string propName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }

    }

UPDATE 2:

My check mechanism:

public bool Validate(object viewModel)
        {
            _brokenRules = new List<BrokenRule>();

            // get all the properties 

            var properties = viewModel.GetType().GetProperties(); 

            foreach(var property in properties)
            {
                // get the custom attribute 

                var attribues = property.GetCustomAttributes(typeof (EStudyValidationAttribute), false); 

                foreach(EStudyValidationAttribute att in attribues)
                {
                    bool isValid = att.IsValid(property.GetValue(viewModel,null));

                    if(isValid) continue; 

                    // add the broken rule 

                    var brokenRule = new BrokenRule()
                                         {
                                             PropertyName = property.Name,
                                             Message = att.Message
                                         }; 

                    _brokenRules.Add(brokenRule);
                }

            }

            var list = _brokenRules.ToObservableCollection(); 

            viewModel.GetType().GetProperty("Errors").SetValue(viewModel,list,null);

            return (_brokenRules.Count() == 0); 
        }

Answer 1

IDataErrorInfo ViewModels, XAML - Validation.HasError ; , .Net.

<Style x:Key="textBoxStyle" TargetType="{x:Type TextBox}">                   

            <Style.Triggers>

                <DataTrigger Binding="{Binding Path=Validation.HasError}" Value="True">
                    <Setter Property="Background" Value="Red" />
                </DataTrigger>

            </Style.Triggers>

        </Style>

TextBoxes ValidatesOnDataError true.

<TextBox x:Name="someTextBox" Text="{Binding Path=someProperty, ValidatesOnDataErrors=True}">



public class ViewModel : ContentControl, INotifyPropertyChanged,IDataErrorInfo
    {
        public event PropertyChangedEventHandler PropertyChanged;

        protected void OnPropertyChanged(string propName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }

        public string this[string propertyName]
        {
            get
            {
                return ValidateProperty(this,propertyName);
            }
        }

        public string Error
        {
            get
            {
                            return "";
            }
        }

    }

, .

Answer 2

WPF Application Framework (WAF) BookLibrary EmailClient. DataAnnotations IDataErrorInfo. (, BookLibrary.Domain/Book.cs).