Custom Validation for Duplicate UserName in DB

If you have better approach to handle custom Validation please let me know. I don't want service layer for this please.

Read below 5th option what I want.

I have

1 - IUserRepository -> bool IsUserRegistered(string userName);

2 - UserRepository with Method

readonly EFDBContainer _db = new EFDBContainer();
public bool IsUserRegistered(string userName)
{
    return _db.Users.Any(d => d.UserName == userName);
}

3 - Ninject --> UserController is DI

public 开发者_Python百科static void RegisterServices(IKernel kernel) 
{
    kernel.Bind<IUserRepository>().To<UserRepositary>();
}

4 - UserController

private readonly IUserRepository _repository;
public ProfileController(IUserRepository repository)
{
    _repository = repository;
}

Create Method on Controller

HttpPost]
public ActionResult Create(string confirmButton, User user)
{
    if (ModelState.IsValid)
    {
        try
        {
            _repository.Create(user); --> This calling Create Method below before this EnsureValid is Called
            return //Do Redirection

        }
        catch (RuleViolationException)
        {
            this.UpdateModelStateWithViolations(user, ViewData.ModelState);
        }
    }
    return //to View;
}

Create Method from Repository

public void Create(User user)
{
    user.EnsureValid(); --> Go to User object and do validation
    //Add object to DB
}

5 - What I want:

Here I want DI so that I can call 1st IsUserRegistered interface method on User object IsUserRegistered below is not working right now. I need a way to use the Interface

public partial class User: IRuleEntity
{
    public List<RuleViolation> GetRuleViolations()
    {
        List<RuleViolation> validationIssues = new List<RuleViolation>();

        if (IsUserRegistered(userName))
            validationIssues.Add(new RuleViolation("UserName", UserName, "Username already exists. Please enter a different user name."));

        return validationIssues;
    }

    public void EnsureValid()
    {
        List<RuleViolation> issues = GetRuleViolations();

        if (issues.Count != 0)
            throw new RuleViolationException("Business Rule Violations", issues);
    }
}

Write your own validation attribute and add it to the user name.

See http://www.planetgeek.ch/2010/11/13/official-ninject-mvc-extension-gets-support-for-mvc3/. It explains how to inject dependencies into validators.

See also the sample application that comes with the Ninject MVC extension it has an example of a validator that has a dependency. https://github.com/ninject/ninject.web.mvc