Question

i am having a problem with the IDataErrorInfo, here is a sample

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = new MainWindowViewModel();
    }
}

public class MainWindowViewModel : INotifyPropertyChanged, IDataErrorInfo
{
    public List<Person> _source1 = null;
    public List<Person> Source1
    {
        get
        {
            return _source1 ?? (_source1 = new List<Person>()
                {
                    new Person(){ Nom ="one"}
                });
        }
    }

    public List<Person> _source2 = null;
    public List<Person> Source2
    {
        get
        {
            return _source2 ?? (_source2 = new List<Person>()
                {
                    new Person(){ Nom ="two"}
                });
        }
    }


    private Person _selectedItem1;
    public Person SelectedItem1 { get { return _selectedItem1; } set { _selectedItem1 = value; RaisePropertyChanged("SelectedItem1"); } }
    private Person _selectedItem2;
    public Person SelectedItem2 { get { return _selectedItem2; } set { _selectedItem2 = value; RaisePropertyChanged("SelectedItem2"); } }

    public MainWindowViewModel()
    {
        //This is the actual way, i solve my problem
        //this.PropertyChanged += (sender, e) =>
        //    {
        //        if (e.PropertyName == "SelectedItem1")
        //        {
        //            RaisePropertyChanged("SelectedItem2");
        //        }
        //    };
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void RaisePropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    public string Error
    {
        get { throw new NotImplementedException(); }
    }

    public string this[string columnName]
    {
        get {

            string errors= string.Empty;

            if (columnName == "SelectedItem2")
            {
                if(this.SelectedItem1 != null && this.SelectedItem2 == null)
                    errors = "erreur";
            }

            return errors;
        }
    }
}

public class Person
{
    public string Nom { get; set; }        
}

As you can see i must inform that the SelectedItem2 is wonder since the SelectedItem1 is selected, but the redcorner does not appear. Here is the xaml code.

<Window x:Class="WpfApplication5.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<StackPanel>
    <ComboBox ItemsSource="{Binding Path=Source1}" DisplayMemberPath="Nom" SelectedItem="{Binding Path=SelectedItem1}"/>
    <ComboBox ItemsSource="{Binding Path=Source2}" DisplayMemberPath="Nom" SelectedItem="{Binding Path=SelectedItem2,ValidatesOnDataErrors=True}"/>
</StackPanel>

Is a better way to solve this problem.

Answer 1

I think all you need to do is

public Person SelectedItem1 
{ 
    get { return _selectedItem1; } 
    set 
    { 
       _selectedItem1 = value; 
       RaisePropertyChanged("SelectedItem1"); 
       RaisePropertyChanged("SelectedItem2"); 
    } 
}

This will cause re-evaluation of validation on SelectedItem2 when SelectedItem1 has been changed.