Async Validation - Calling server validation from client async

Lets define our example:

• Project name: SLUsers
• Domain Service: Domain
• Entity: Users
•  UserID
•  UserName
•  Password

We need to check the availability of the UserName while the person is still filling the registration form.


Step #1

======

In the Server App, in your Domain Service create the following :

        [Invoke]

        public bool IsUserNameUsed(string userName)

        {

            Users _users = null;

            using (DomainEntities domainEntity = new DomainEntities())

            {

                _users = domainEntity.Users.Where(s => s.UserName == userName).SingleOrDefault();

            }

            return _users != null;

        }

 

 

Step #2

======

In the Silverlight Client App, in the Model folder add new class and paste the following:

 

 

using System.ComponentModel.DataAnnotations;

using SLUsers.Web.Services;

using System.ServiceModel.DomainServices.Client;

namespace SLUsers.Web.Models

{

    public partial class Users

    {

        private ValidationResult _isUserNameUsedValidationResult;

        partial void OnUserNameChanged()

        {

           if (IsDeserializing)

               return;

            DomainContext context = new DomainContext();

            context.IsUserNameUsed(UserName,

                delegate(InvokeOperation<bool> isUsed)

                {

                    if (isUsed.Value)

                    {

                        _isUserNameUsedValidationResult = new ValidationResult("Username already exist in database !", new string[] {"UserName"});

                         

                        ValidationErrors.Add(_isUserNameUsedValidationResult);

                    }

                }, null);

        }

         

    }

}

 

 

 

Notes

=====

1- The class created in Step #2 in the client application have the name space SLUsers.Web.Models which referes to the Web.

2- The part which triggers the validation lies in the step #2 in the line:

 _isUserNameUsedValidationResult = new ValidationResult("Username already exist in database !", new string[] {"UserName"});

 where the field name to be validated is 'Username' as:

  new string[] {"UserName"}.

3- In XAML page binding, don't forget to raise the validation error as:

 Text="{Binding Path=UserName, Mode=TwoWay, NotifyOnValidationError=True, UpdateSourceTrigger=PropertyChanged}"

Have a nice day :)