How do you set the Customvalidation in Metadata file, If the Metadata is in different Model project - wcf

Question

My silverlight solution has 3 project files
Silverlight part(Client)
Web part(Server)
Entity model(I maintained the edmx along with Metadata in a seperate project)
Metadata file is a partial class with relavent dataannotation validations.
[MetadataTypeAttribute(typeof(User.UserMetadata))]
public partial class User
{
[CustomValidation(typeof(UsernameValidator), "IsUsernameAvailable")]
public string UserName { get; set; }
}
Now my question is where I need to keep this class UsernameValidator
If my Metadata class and edmx are on Server side(Web) then I know I need to create a .shared.cs class in my web project, then add the proper static method.
My IsUserAvailable method intern will call a domainservice method as part of asyc validation.
[Invoke]
public bool IsUsernameAvailable(string username)
{
return !Membership.FindUsersByName(username).Cast<MembershipUser>().Any();
}
If my metadata class is in the same project as my domain service is in then I can call domain service method from my UsernameValidator.Shared.cs class.
But here my entity models and Metadata are in seperate library.
Any idea will be appreciated
Jeff wonderfully explained the asyc validation here
http://jeffhandley.com/archive/2010/05/26/asyncvalidation-again.aspx
but that will work only when your model, metadata and Shared class, all are on server side.

Answer 1

There is a kind of hack to do this. It is not a clean way to do it it, but this is how it would probably work.
Because the .shared takes care of the code generation it doesn't complain about certain compile errors in the #if brackets of the code. So what you can do is create a Validator.Shared.cs in any project and just make sure it generates to the silverlight side.
Add the following code. and dont forget the namespaces.
#if SILVERLIGHT
using WebProject.Web.Services;
using System.ServiceModel.DomainServices.Client;
#endif
#if SILVERLIGHT
UserContext context = new UserContext();
InvokeOperation<bool> availability = context.DoesUserExist(username);
//code ommited. use what logic you want, maybe Jeffs post.
#endif
The compiler will ignore this code part because it does not meet the condition of the if statement. Meanwhile on the silverlight client side it tries to recompile the shared validator where it DOES meet the condition of the if-statement.
Like I said. This is NOT a clean way to do this. And you might have trouble with missing namespaces. You need to resolve them in the non-generated Validator.shared.cs to finally let it work in silverlight. If you do this right you can have the validation in silverlight with invoke operations. But not in your project with models and metadata like you would have with Jeff's post.
Edit: I found a cleaner and better way
you can create a partial class on the silverlight client side and doing the following
public partial class User
{
partial void OnUserNameChanging(string value)
{
//must be new to check for this validation rule
if(EntityState == EntityState.New)
{
var ctx = new UserContext();
ctx.IsValidUserName(value).Completed += (s, args) =>
{
InvokeOperation invop = (InvokeOperation) s;
bool isValid = (bool) invop.Value;
if(!isValid)
{
ValidationResult error = new ValidationResult(
"Username already exists",
new string[] {"UserName"});
ValidationErrors.Add(error;
}
};
}
}
}
This is a method generated by WCF RIA Services and can be easily partialled and you can add out-of-band validation like this. This is a much cleaner way to do this, but still this validation now only exists in the silverlight client side.
Hope this helps