CODEWITHSUNDEEP
c#wpfmvvm
Paul Miranda
Paul Miranda

Reputation: 748

Textbox not setting the value as null when the user cleans the text field in WPF

I have the next textbox:

<TextBox FontSize="10">
    <TextBox.Text>
        <Binding Path="EstatusAdministrativo" ValidatesOnDataErrors="True" UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <validations:IsRequiredValidationRule />
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

This textbox is binded to a variable in the ViewModel that looks like this:

private string _EstatusAdministrativo;
public string EstatusAdministrativo {
 get {
  return _EstatusAdministrativo;
 }
 set {
  _EstatusAdministrativo = value;
  OnPropertyChanged();
 }
}

The validation inside of the textbox looks like this:

public class IsRequiredValidationRule: ValidationRule {
 public override ValidationResult Validate(object value, CultureInfo cultureInfo) {
  string strValue = Convert.ToString(value);
  if (string.IsNullOrWhiteSpace(strValue))
   return new ValidationResult(false, $ "Por favor llenar este campo.");
  return new ValidationResult(true, null);
 }
}

When I delete all the characters in the textbox, the value of EstatusAdministrativos is not setting as null. It doesn't trigger the set method when I clean the textbox. Why is this happening and how can I solve it?

Upvotes: 3

Views: 1225

Answers (3)

mm8
mm8

Reputation: 169200

The source property isn't set when the validation rules fails unless you set the ValidationStep property to UpdatedValue:

<validations:IsRequiredValidationRule ValidationStep="UpdatedValue" />

This will cause the validation rule to run after the source property has been set. You can read more about this in this blog post.

If you need more control, you should get rid of the validation rule and implement the INotifyDataErrorInfo interface in your view model class.

Upvotes: 2

blindmeis
blindmeis

Reputation: 22445

instead of 

return new ValidationResult(true, null);

you should call

return ValidationResult.ValidResult;

Upvotes: 1

iej
iej

Reputation: 46

You may need to set ValidatesOnDataErrors = false. This could be preventing the textbox from updating the property value if the entered value does not validate.

https://learn.microsoft.com/en-us/dotnet/api/system.windows.data.binding.validatesondataerrors?view=netframework-4.8

Upvotes: 1

Related Questions