How to bind classes with required connection string in constructor using Ninject?

Question

Here are the classes that I am using:

AppService class:

using SomeProject.LayerB;

namespace SomeProject.LayerA;
{
    public class AppService
    {
        private readonly ISomeRepository someRepository;

        public LocationManagementService(ISomeRepository someRepository)
        {
            this.someRepository = someRepository;
        }

        // other codes ...
    }  
}

SomeRepository class:

namespace SomeProject.LayerB;
{
    public class SomeRepository : ISomeRepository
    {
        private readonly SomeDbContext context;

        public SomeRepository(SomeDbContext context)
        {
            this.context = context;
        }

        // other codes ...
    }
}

SomeDbContext class:

namespace SomeProject.LayerB;
{
    public class SomeDbContext : DbContext
    {
        public SomeDbContext(string nameOrConnectionString)
            : base(nameOrConnectionString)
        {
        }

        // other codes ...
    }  
}

Then, I use a Ninject module containing the following code:

namespace SomeProject.LayerC;  
{
    public class SomeModule : NinjectModule
    {
        public override void Load()
        {
            Bind<ISomeRepository>().To<SomeRepository>();

            // My problem is on this part.. I want to provide the connection string on the
            // main program, not here on this class.
            // Bind<SomeDbContext>().ToSelf().WithConstructorArgument("nameOrConnectionString", "the connection string I want to inject");
        }
    } 
}

Main program:

using SomeProject.LayerA;
using SomeProject.LayerC;

namespace SomeProject.LayerD;
{
    public class MainProgram
    {
        public MainProgram()
        {
            IKernel kernel = new StandardKernel(new SomeModule());

            AppService appService = kernel.Get<AppService>();
        }
    }  
}

NOTE: The only layer that main program can reference is LayerA where AppService class is located and as well as LayerC where the ninject module is found.

The error here is that use your container's auto-wiring capabilities to build up a framework type (your SomeDbContext). As described here, you should register that SomeDbContext using a lambda so that your code calls SomeDbContext's constructor. — Steven

Sam FarajpourGhamari Sam FarajpourGhamari · Accepted Answer · 2015-07-25T08:13:06

Add a Configuration class like this:

public class Config
{
    public static string ConnectionString { get; set; }
}

and in your ninject module write this:

Bind<SomeDbContext>().ToSelf()
   .WithConstructorArgument("nameOrConnectionString", 
       c => Config.ConnectionString);

then in your main method you could write following:

public class MainProgram
{
    public MainProgram()
    {
        IKernel kernel = new StandardKernel(new SomeModule());
        Config.ConnectionString = "The connection string";
        AppService appService = kernel.Get<AppService>();
    }
}

Update:

You can use ninject to locate config class also if you don't want use static methods:

class Config2
{
    public string ConnectionString { get; set; }
}

in module:

Bind<Config2>().ToSelf().InSingletonScope();
Bind<SomeDbContext>().ToSelf()
   .WithConstructorArgument("nameOrConnectionString",
       c=>c.Kernel.Get<Config2>().ConnectionString);

in main:

IKernel kernel = new StandardKernel(new SomeModule());
var conf = kernel.Get<Config2>();
conf.ConnectionString = "The connection string";
AppService appService = kernel.Get<AppService>();

How to bind classes with required connection string in constructor using Ninject?

1 Answers