Validation

In order DataForm to support validation the developer must implement the ISupportEntityValidation interface. This validator should be passed through the (link)EntityProvider GetItemValidator method. The ValidateAsync method of this interface will be called from the RadDataForm depending on the RadDataForm.ValidationMode value.

The ISupportEntityValidation interface derrives from the well known INotifyDataErrorInfo, so the methodology is the same. The developer should implement GetErrors method, HasErrors property and should raise the ErrorsChanged event when the errors has been changed. Additionally when validation is needed the ValidatePropertyAsync method(which recieves the Entity object and the propertyName of the EntityProperty that should be validated) will be called.

• OnCommit - Validation will be triggered when an EntityProperty tries to commit a value.
• Immediate - Validation will be triggered whenever the user changes the value candidate.
• OnLostFocus - Validation will be triggered when the editor loses focus.

Example

Let's have the following DataForm definition:

<data:RadDataForm x:Name="DataForm" Item="{Binding}" CommitMode="OnLostFocus" ValidationMode="OnCommit"/>

Here is the used Item class that should implement ISupportEntityValidation:

public class Item : ViewModelBase, ISupportEntityValidation
{
    Dictionary<string, List<string>> errors = new Dictionary<string, List<string>>();

    private string name;
    public string Name
    {
        get { return this.name; }
        set { this.name = value; OnPropertyChanged("Name"); }
    }

    private double age;

    public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;

    public double Age
    {
        get { return this.age; }
        set { this.age = value; OnPropertyChanged("Age"); }
    }

    public bool HasErrors
    {
        get
        {
            return this.errors.Count > 0;
        }
    }

    public Task ValidatePropertyAsync(Entity entity, string propertyName)
    {
        if (propertyName.Equals("Age"))
        {
            var property = entity.GetEntityProperty(propertyName);
            double value;
            Double.TryParse(property.PropertyValue.ToString(), out value);

            if (value < 18)
            {
                this.errors[propertyName] = new List<string>() { "Age under 18 is not allowed!" };
            }
            else
            {
                this.errors[propertyName] = new List<string>();
            }

            this.ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
        }
        else if (propertyName.Equals("Name"))
        {
            var name = entity.GetEntityProperty(propertyName).PropertyValue.ToString();
            if (String.IsNullOrEmpty(name))
            {
                this.errors[propertyName] = new List<string>() { "The Name cannot be empty!" };
            }
            else
            {
                this.errors[propertyName] = new List<string>();
            }

            this.ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
        }


        return null;
    }

    public IEnumerable GetErrors(string propertyName)
    {
        if (this.errors.ContainsKey(propertyName))
        {
            return this.errors[propertyName];
        }

        return new List<string>();
    }
}

Lastly, set the Item class as DataContext of the DataForm:

this.DataContext = new Item() { Name = "Ivaylo", Age = 17 };

Here is the result: