Adding Data Validation with IValidatableObject to Entity Framework entities in WPF and C#

Question

I´m doing an app in WPF, C# and EntityFramework 4.0.

I have to validate a date and I would like to show the user if the date is after today something like this:

http://www.nbdtech.com/images/blog/20100621/NiceValidation.png

My code is:

In LoanWindow.xaml:

 <!-- In my window resources -->
      <Style x:Key="datoNoValido" TargetType="{x:Type DatePicker}">
                <Style.Triggers>
                    <Trigger Property="Validation.HasError" Value="true">
                        <Setter Property="ToolTip"  Value="Wrong Date"/>
                    </Trigger>
                </Style.Triggers>
            </Style>

    <!-- After some code in the Grid -->
        <DatePicker Style="{StaticResource datoNoValido}" 
                    Name="fecha_SalidaDatePicker" 
                    SelectedDate="{Binding Path=Fecha_Salidad, Mode=TwoWay, ValidatesOnExceptions=true, NotifyOnValidationError=true, UpdateSourceTrigger=PropertyChanged}" />

My partial class:

public partial class Loan : IValidatableObject
{
    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (DateTime.Compare(MyDate, DateTime.Now.Date) < 0)
        {
            ValidationResult vr = new ValidationResult("the message", new[] { "MyDate" });
            this.validationErrors.Add(vr);
        }
        return this.validationErrors;
    }
}

In LoanWindow.xaml.cs:

 //Some code and after
 var errors = p.Validate(null);
 foreach (var item in errors)
 {
   MessageBox.Show(item.ErrorMessage);
 }

The message defined in the partial class (match the name of the entity framework class) shown´s up, but the datapicker never shows the red line. What I´m doin wrong? How should I do it?

Thnks.

Answer 1

On the SelectedDate property the only odd thing i see is that you are not setting the property

    ValidatesOnDataErrors=True

this works for me