Thanks for the latest sample.

          If I make a Company Name error by entering @ as part of the name, it shows the error correctly, but as mentioned earlier the error is duplicated if I tab back to the same field. After correcting the error, the user is expected to come back to the filed twice to clear all the existing errors. Do you still think it is the problem with DataGrid/INotifyDataErrorInfo? If so, do you know why we do not see such a behavior when doing Synchronous Validations?

         Also, the ValidationError is removed by checking for '@' in the error message. It is possible that we might have such characters in other error messages or we may not have such a text to look for in our messages. Is there a better implementation for this? Is there a tag property or something like that for validation error which we can set when a specific error message is generated (may be, a unique Message ID) so that we can look for such immutable property and remove those errors.

          For example, if we have validations to make sure that Name and ID must be unique (checked async), the messages might be just 'Must be Unique'  or 'ID must be unique.' or 'Description must be unique.'. It might be difficult to remove such messages. Another alternative might be to regenerate the same message and look for its existence and remove it. However, this won’t work if we have generic messages like ‘Must be unique’ and the context is added dynamically as part of displaying error summary.

          Thanks again for your help.

           I tried this solution and it works with adding validationresults to the collection. 

           However, if the same error occurs again for adifferent value for the same property (after the initial error), the error isadded again to the validation summary control unlike the Verifier Engine behavior, which is onlyone entry in the Validation Summary even if the same verifier error occurs forthe same property multiple times.  Do we need to have custom logic toavoid getting duplicate messages?

On a similar note, how do we remove the message after the Asynccall succeeds? If I try to remove the validation error by callingEntityAspect.ValidationErrors.Remove(), the message is removed from thecollection, but the property still shows as in error and the ValidationSummaryalso shows the error.  Do we need to doanything else apart from removing the validation result from theValidationErrors collection?

Thanks.

         For example, let us sayAsync Check Unique validators are defined for ID and Name properties onEmployee. When the Check Unique validation for ID fails, the callback specifiedwill know the context, but how can this context information be passed to theVerifierEngine so that the ID property can be marked as in error (red boxaround) and show the error message when hovering over the box (as done byInotifyDataErrorInfo).

           In the callbackmethod, if I just create a verifier result how will the Validation Engineknow that the error is for ID and not for Name? I was thinking that in thiscase Target needs to be set to “ID” in the VerifierResult so that it can be markedas in error. Can you please clarify?

 Thanks

 Sample pseudo-code:

ValidatorMethod (…)

{

        …

        /* Async Queryto check for duplicate values in the database */

                   EntityManager.ExecuteQueryAsync(query, userCallback, userState)

        …

}

userCallback(…)

{

            …

            _verifierResult = new VerifierResult(_result, message);            

           _currInstance.EntityAspect. ValidationErrors.Add(_verifierResult);

            …

}