Question

I’m trying to use a custom role provider in an MVC3 app. I’ve already got the membership provider working ok using Ninject but can’t seem to get the role provider working. The Membership provider doesn’t require a parameterless constructor but role provider does. Here’s some code snippets:

Web.config

<membership>
  <providers>
    <clear/>
    <add name="MyMembershipProvider" type="MyApp.Models.NHibernateMembershipProvider" 
         applicationName="myApp" />
  </providers>
</membership>

<roleManager enabled="true">
  <providers>
    <add name="MyRolesProvider" type="MyApp.Models.NHibernateRoleProvider"
         applicationName="myApp" />
  </providers>
</roleManager>

I have a Ninject module.

public class MyNinjectModule : NinjectModule
{
    public override void Load()
    {
        this.Bind<ISession>().ToMethod(
            x => MyApp.MvcApplication.SessionFactoryData.GetCurrentSession());

        // Respository
        this.Bind<IUserRepository>().To<UserRepository>();
        this.Bind<MembershipProvider>().To<NHibernateMembershipProvider>();
        this.Bind<RoleProvider>().To<NHibernateRoleProvider>();
    }
}

The custom Membership provider

public class NHibernateMembershipProvider : MembershipProvider
{
    private IUserRepository _repo;

    public NHibernateMembershipProvider(IUserRepository repository)
    {
        _repo = repository;
    }
    ...

The role provider

public class NHibernateRoleProvider : RoleProvider
{

    private IUserRepository _repo;

    public NHibernateRoleProvider(IUserRepository repository)
    {
        _repo = repository;
    }
    ...

I then configure my controller to require an authorize

    [Authorize(Roles="Admin")]
    public ActionResult Edit(int? id)
    {
       ...

I get this error when starting the app.

Parser Error Message: No parameterless constructor defined for this object.

Source Error: 


Line 49:     <roleManager enabled="true">
Line 50:       <providers>
Line 51:         <add name="MyRolesProvider" type="MyApp.Models.NHibernateRoleProvider"
Line 52:              applicationName="myApp" />
Line 53:       </providers>

I can access the users through the membership provider, so the repository is being injected ok, but the roles provider seems to be different. Why does the role provider require a constructor-less parameter? Is there a simple way to get the role provider to work with Ninject. Any help appreciated.

Answer 1

Since the role provider, in this case the NHibernateRoleProvider is instantiated by the ASP.NET framework the best solution is to use the service locator pattern. The service locator pattern is normally considered to be an anti-pattern but sometimes you have to be pragmatic and accepted the limitation on the framework that is being used (in this case the ASP.NET framework).

Assuming you are using an implementation of the IDependencyResolver interface for Ninject. The following code should work.

public class NHibernateMembershipProvider : MembershipProvider
{
    private IUserRepository _repo;

    public NHibernateMembershipProvider()
    {
        _repo = DependencyResolver.Current.GetService<IUserRepository>();
    }

    // ...
}