How to remove one or more fields from the DataForm.Validating() event in Silverlight 4?

Question

I have a data form that is bound to an object whose properties are decorated with System.ObjectModel.DataAnnotation attributes for validaton.

The problem I am facing is that some properties of this class are only conditionally needed and do not need to be validated. For example when an admin of the app decides to edit a user, he or she may enter a password/password confirm/password question/password answer. Or he/she may entirely skip those properties.

So if the admin decides to enter any of those 4 fields, they all have to be present and the validation rules for all these fields have to be applied. However if the admin only wants to change the FirstName, LastName, Email, or whatever other arbitrary properties - the password related fields do not need to be validated.

Is there a way to "Exclude" them from the validation process?

this is a sample of the object I work with:

public class RegistrationData
{
   public string FirstName { get; set; }
   public string LastName { get; set; }
   public string Email { get; set; }
   public string Username { get; set; }
   public string Password { get; set; }
   public string PasswordConfirm { get; set; }
   public string PasswordQuestion { get; set; }
   public string PasswordAnswer { get; set; }
}

I have a DataForm called registrationForm in the Xaml and the error I get is in this code:

private void RegistrationButton_Click(object sender, RoutedEventArgs e)
{
   if( this.registerForm.ValidateItem() )
   {
       //Does not pass validaton if the password properties are not filled in.
   }
}

Any ideas on how to fix it?

I was thinking of using two DataForms... and split the user object in two, but that involves a lot of code...

May I ask how are you performing your validation? More precisely are you using any of the predefined interfaces for error notification? I am asking because it seems like you are not using the registration data class for that so where is it happening? — Stainedart, May 17 '12 at 17:43
@Stainedart: Yes, we use a Silverlight DataForm and the annotation properties. For new user's I would like to enter the password, when I edit user's the password field should not be validated. In my case I would be happy with a solution just to disable validation. — slfan, May 18 '12 at 06:07
@slfan if you look at my answer below using a different way than data annotation would allow you to have the flexibility of validation you require. — Stainedart, May 18 '12 at 12:38

score 1 · Answer 1 · edited May 22 '12 at 05:57

I would recommend to use the INotifyDataError interface on your RegistrationData object.

    public string LabelWrapper
    {
        get
        {
            return this.Label;
        }
        set
        {
            ValidateRequired("LabelWrapper", value, "Label required");
            ValidateRegularExpression("LabelWrapper", value, @"^[\w-_ ]+$", "Characters allowed (a-z,A-Z,0-9,-,_, )");
            this.Label = value;
            this.RaisePropertyChanged("LabelWrapper");
        }
    }

    public string DependentLabelWrapper
    {
        get
        {
            return this.DependentLabel;
        }
        set
        {
            if(LabelWrapper != null){
                ValidateRequired("DependentLabelWrapper", value, "Label required");
                ValidateRegularExpression("LabelWrapper", value, @"^[\w-_ ]+$", "Characters allowed (a-z,A-Z,0-9,-,_, )");
             }
            this.DependentLabel = value;
            this.RaisePropertyChanged("DependentLabelWrapper");
        }
    }

I recommend you to look at this link http://blogs.msdn.com/b/nagasatish/archive/2009/03/22/datagrid-validation.aspx to learn more about different validation types.

Also MSDN has a nice explanation on how to use it

http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifydataerrorinfo%28VS.95%29.aspx

Thanks for your input. I know the INotifyDataError interface. It's a lot of code to write. All I want is to temporarily disable a validation attribute. — slfan, May 22 '12 at 06:00

score 1 · Answer 2 · edited May 23 '17 at 10:26

This question brought me to another solution. I now use CustomValidation:

[CustomValidation(typeof(RegistrationDataValidation), "ValidatePassword")]
public class RegistrationData  
{  
    public bool IsNewUser { get; set; }
     ... // other registration properties
}  

public static class RegistrationDataValidation
{
    public static ValidationResult ValidatePassword(MembershipServiceUser user, ValidationContext context)
    {
        if (user.IsNewUser && string.IsNullOrEmpty(user.Password))
        {
            return new ValidationResult("Password required");
        }
        return ValidationResult.Success;
    }
}

I added a property IsNewUser which I set in the client when adding a new user. The custom validation method checks this property and executes the desired validation. I still have a RegularExpression Attribute on the password which will be validated as well.

In comparison to @Staindart's solution this is checked on the client synchronously.

score 0 · Answer 3 · answered Jun 19 '12 at 07:34

The simplest and ugliest way would be to tap into the DataForm.ValidatingItem event. Like so:

    void dfEditForm_ValidatingItem(object sender, System.ComponentModel.CancelEventArgs e)
    {
        foreach (ValidationSummaryItem item in dfEditForm.ValidationSummary.Errors)
        {
            if (item.Sources.Where(W => W.PropertyName != "myIgnoredPropertyName").Count() > 0)
                e.Cancel = true;
        }
    }

How to remove one or more fields from the DataForm.Validating() event in Silverlight 4?

3 Answers3