CODEWITHSUNDEEP
c#wpfvalidationidataerrorinfo
coder_bro
coder_bro

Reputation: 10773

IDataErrorInfo : Not validating input

I have a user control which contains a textbox. I have a class called Person which implements IDataErrorInfo interface:

class Person : IDataErrorInfo
{
private bool hasErrors = false;
#region IDataErrorInfo Members

        public string Error
        {            
            get 
            {
                string error = null;
                if (hasErrors)
                {
                    error = "xxThe form contains one or more validation errors";
                }
                return error;
            }
        }

        public string this[string columnName]
        {
            get 
            {
                return DoValidation(columnName);
            }
        }
        #endregion
}

Now the usercontrol exposes a method called SetSource through which the code sets the binding:

public partial class TxtUserControl : UserControl 
    {          
        private Binding _binding;

        public void SetSource(string path,Object source)
        {
            _binding = new Binding(path);
            _binding.Source = source;
            ValidationRule rule;
            rule = new DataErrorValidationRule();
            rule.ValidatesOnTargetUpdated = true;            
            _binding.ValidationRules.Add(rule);
            _binding.ValidatesOnDataErrors = true;
            _binding.UpdateSourceTrigger = UpdateSourceTrigger.LostFocus;
            _binding.NotifyOnValidationError = true;            
            _binding.ValidatesOnExceptions = true;
            txtNumeric.SetBinding(TextBox.TextProperty, _binding);                
        }
...
}

The WPF window that includes the user control has the following code:

public SampleWindow()
    {
        person= new Person();
        person.Age = new Age();
        person.Age.Value = 28;

        numericAdmins.SetSource("Age.Value", person);
    }
    private void btnOk_Click(object sender, RoutedEventArgs e)
    {         

        if(!String.IsNullOrEmpty(person.Error))
        {
            MessageBox.Show("Error: "+person.Error);
        }
    }

Given this code, the binding is working fine, but the validation never gets triggered. Whats wrong with this code?

Upvotes: 1

Views: 3390

Answers (2)

Ignacio Soler Garcia
Ignacio Soler Garcia

Reputation: 21855

Another option could be to implement IDataErrorInfo on the Age class and create an event on it like OnValidationRequested that should be captured by the Person class. This way you could validate the Age field based on other properties of the Person class.

Upvotes: 0

Paul Stovell
Paul Stovell

Reputation: 32715

Your Age class will need to implement IDataErrorInfo. Your Person class won't be asked to validate the Age's properties.

If that is not an option, I wrote a validation system for WPF that is extensible enough to support this. The URL is here:

In the ZIP is a word document describing it.

Edit: here's one way age could implement IDataErrorInfo without being too smart:

class Constraint 
{
    public string Message { get; set; }
    public Func<bool> Validate;
    public string Name { get; set; }
}

class Age : IDataErrorInfo
{
    private readonly List<Constraint> _constraints = new List<Constraint>();

    public string this[string columnName]
    {
        get 
        {
            var constraint = _constrains.Where(c => c.Name == columnName).FirstOrDefault();
            if (constraint != null)
            {
                if (!constraint.Validate())
                {
                    return constraint.Message;
                }
            }
            return string.Empty;
        }
    }
}

class Person
{
    private Age _age;

    public Person() 
    {
        _age = new Age(
            new Constraint("Value", "Value must be greater than 28", () => Age > 28);
    }
}

Also see this link:

http://www.codeproject.com/KB/cs/DelegateBusinessObjects.aspx

Upvotes: 3

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