How to inject a parameter constructor into Repository constructor using Ninject?

Question

I am trying to create DBContect object by passing connection string at run time. Following is the structure of my NiNject Repository implementation.

public class HomeController : ApiController
{
    MyService _service{ get; set; }

    public HomeController(MyService service)
    {
        _service= service;
    }
}

public class MyService 
{
    IRepository _repo { get; set; }

    public MyService(IRepository repo)
    {
        _repo = repo;
    }
}

Repository implementation is as follows :

public interface IRepository
{
    TenantDbContext _db { get; set; }
    void Add<T>(T entity) where T : class;
    void Delete<T>(int id) where T : class;
    T Find<T>(int id) where T : class;
    IQueryable<T> Query<T>() where T : class;
    void SaveChanges();

    MasterDbContext _db_master { get; set; }
    void Add_Master<T>(T entity) where T : class;
    void Delete_Master<T>(int id) where T : class;
    T Find_Master<T>(int id) where T : class;
    IQueryable<T> Query_Master<T>() where T : class;
    void SaveChanges_Master();
}

public class Repository : IRepository
{
    public TenantDbContext _db { get; set; }
    public MasterDbContext _db_master { get; set; }

    public Repository(TenantDbContext db)
    {
        _db = db;
    }
    public Repository(MasterDbContext db_master)
    {
        _db_master = db_master;
    }
    public IQueryable<T> Query<T>() where T : class
    {
        return _db.Set<T>().AsQueryable();
    }
    public IQueryable<T> Query_Master<T>() where T : class
    {
        return _db_master.Set<T>().AsQueryable();
    }
//.....Rest of the implemetation
}

Here goes my TenantDBContext class which takes an argument as a database string. No default constructor

 public class TenantDbContext : DbContext
{
    public TenantDbContext(string connString)
        : base(connString)
    {
        //Configuration.AutoDetectChangesEnabled = true;
        //Configuration.LazyLoadingEnabled = false;
        //Configuration.ProxyCreationEnabled = false; //change tracking 
    }

    public static TenantDbContext Create(string DbString)
    {
        // Some logic to get the tenant database string. 
        // Presently i am just passing it hard coded as follows.

        return new TenantDbContext(DbString);
    }
}
public class MasterDbContext : IdentityDbContext<ApplicationUser>
{
    public MasterDbContext() : base("MasterDBConnection", throwIfV1Schema: false)
    {
       // dbmigration.AutomaticMigrationsEnabled = true;
        Configuration.ProxyCreationEnabled = false;
        Configuration.LazyLoadingEnabled = false;
    }
    public static MasterDbContext Create()
    {
        return new MasterDbContext();
    }

    //public DbSet<ApplicationUser> ApplicationUsers { get; set; }
    public DbSet<Tenant> Tenants { get; set; }
    public DbSet<TenantUserMap> TenantUserMaps { get; set; } }

Finally, RegisterServices which i have in my NinjectWebCommons.cs looks as follows : Each Tenant have its different database. We are fetching out the Tenant name from the access token on every request and caching that requested Tenant object so we can pass the correct Tenant Database string in order to do the operations on the requested Tenant Database.

Below snippet, We are fetching the Tenant object from the current request cache which will provide us the Tenant Database string of the requested client.

 public Tenant Tenant
    {
        get
        {
            object multiTenant;
            if (!HttpContext.Current.GetOwinContext().Environment.TryGetValue("MultiTenant", out multiTenant))
            {
                throw new ApplicationException("Could Not Find Tenant");
            }
            return (Tenant)multiTenant;
        }
    }

private static void RegisterServices(IKernel kernel)
    {
        kernel.Bind<IRepository>().To<Repository>();
        kernel.Bind<TenantDbContext>().ToMethod(_ => 
        TenantDbContext.Create(Tenant.DBString)); 
        kernel.Bind<MasterDbContext>().ToMethod(__ => MasterDbContext.Create());
    }   

Problem : When i add second binding in my NinjectWebCommons.cs "kernel.Bind()" , i start getting exception saying that "No default constructor found". It is simply not taking two bindings with the kernal. Request you to please have a look at the code above and point me out where i am going wrong.

I will appreciate your help. Thanks in Advance.

Answer 1

You may add a binding for the database context and point Ninject to use your factory method:

kernel.Bind<TenantDbContext>().ToMethod(_ => TenantDbContext.Create());