Question

I am very new to Ninject and am trying Ninject 2 with MVC and Linq. I have a SqlProductRepository class and all I want to know is what s the best way of passing the connectionstring in the constructor if I am injecting the Repository object in the controller.

public class SqlProductRepository:IProductRepository
{
    private Table<Product> productsTable;

    public SqlProductRepository(string connectionString)
    {
      productsTable = (new DataContext(connectionString)).GetTable<Product>();   
    }

    public IQueryable<Product> Products
    {
        get { return productsTable; }
    }
}

This is my ProductController class where I am injecting the Repository:

  public class ProductsController : Controller
{
    private int pageSize = 4;
    public int PageSize { get { return pageSize; } set { pageSize = value; } }  

    IProductRepository _productsRepository;

    [Inject]
    public ProductsController(IProductRepository productRepository)
    {
        _productsRepository = productRepository;
    }

    public ViewResult List(int page)
    {
        return View(_productsRepository.Products
                                       .Skip((page - 1) * pageSize)
                                       .Take(pageSize)
                                       .ToList()
                    );
    }
}

Can somebody please guide me regarding this?

Answer 1

You can set it up in your binding


_kernel.Bind<IProductRepository>()
       .To<SqlProductRepository>()
       .WithConstructorArgument("connectionString",yourConnectionString );

Answer 2

You re doing:

new DataContext(connectionString)

in your code - this is the very newing and binding to classes you re trying to push out of your code by using a DI container. At the very least, consider adding an IConnectionStringSelector interface or something like that. You dont want to have 20 Bind calls for 20 repositories - you want a higher level abstraction than that.

I d suggest the best solution is that you should be demanding either an IDataContext or an IDataContextFactory in the constructor instead and letting that worry about it.

Answer 3

You could supply the connection string as a constructor argument when binding the SqlProductRepository to the IProductRepository interface.

public class LinqToSqlModule : NinjectModule
{
    public override void Load()
    {
        Bind<IProductRepository>().To<SqlProductRepository>()
            .WithConstructorArgument(connectionString, "connectionstring");
    }
}

I would suggest a slightly different approach. First of all, you might want to create a binding for the DataContext class in the kernel. You could do so by using a provider class to create your DataContext passing the connection string as an argument to its constructor. Then you bind the DataContext to the DataContextProvider.

public class DataContextProvider : Provider<DataContext>
{
    protected override DataContext CreateInstance(IContext context)
    {
        string connectionString = "connectionstring";
        return new DataContext(connectionString);
    }
}

public class LinqToSqlModule : NinjectModule
{
    public override void Load()
    {
        Bind<DataContext>().ToProvider<DataContextProvider>();
        Bind<IProductRepository>().To<SqlProductRepository>();
    }
}

Next modify the constructor of SqlProductRepository class to accept a DataContext object instead.

public class SqlProductRepository : IProductRepository
{
    private readonly DataContext context;

    public ProductRepository(DataContext context)
    {
        this.context = context;
    }

    public IQueryable<Product> Products
    { 
        get { return context.GetTable<Product>(); }
    }
}

By the way you don t have to decorate your constructor with the Inject attribute. Ninject will select the constructor with the most parameters by default.

Answer 4

Please refer below code snap:

    //Bind the default connection string
    public void BindDataContext()
    {
        ConstructorArgument parameter = new ConstructorArgument("connectionString", "[Config Value]");
        Bind<DataContext>().ToSelf().InRequestScope().WithParameter(parameter);
    }
    //Re-Bind the connection string (in case of multi-tenant architecture)
    public void ReBindDataContext(string cn)
    {
         ConstructorArgument parameter = new ConstructorArgument("connectionString", cn);
         Rebind<DataContext>().ToSelf().InRequestScope().WithParameter(parameter);
    }

For more information, please visit below link

MVC3, Ninject and Ninject.MVC3 problem

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