Question

I am performing validation based on attributes in metadata.cs file. I am using Entity framework 4.0 and using wcf ria services. I want to know what is the equivalent of Page.IsValid in asp.net in silverlight? How do i ensure that the entity is in correct state before saving it? If i do not ensure this an exception fires which looks very ugly. I found a property named entityName.ValidationErrorCount so if my entity is named User i do objUser.ValidationErrorCount is less than equal to 0 i save it. Problem with this approach is if the user doesn’t enter value in any of the textbox then subsequently all the values in the entity are null. So ValidationErrorCount property returns 0 because all are null values and thus my program tries to save the entity but naturally the entity is in incorrect state so exception fires. How do i get past this problem?

I hope i am clear. If not, please let me know. Thanks in advance 🙂

Answer 1

You can validate an entity using the Validator class (from the System.ComponentModel.DataAnnotations
namespace), like so (where entity is a reference to the entity to be validated):

List<ValidationResult> validationResults = new List<ValidationResult>();
ValidationContext validationContext = new ValidationContext(entity, null, null);
bool isValid = Validator.TryValidateObject(entity, validationContext, validationResults, true);

Alternatively, are you using the DataForm control? If so, there’s an even easier way to check whether the current item is valid, by calling the ValidateItem() method on the DataForm. This will return a boolean indicating whether the current item is valid (you can also check the IsItemValid property of the DataForm). It will also update the bound controls to show their validation status. If you’re not using the DataForm, then it will certainly make it easier if you can. Otherwise, simply add the validation results to the entity’s ValidationErrors property:

foreach (ValidationResult result in validationResults)
    entity.ValidationErrors.Add(result);

Hope this helps…

Chris