Null object when Injecting Repository with Asp.Net Core 2

Question

I can't get my Func to pass across successfully. I inject into the webapi in my startup.cs

services.AddDbContext<MyDataContext>(
    options => options.UseSqlServer(DbGlobals.DevDatabase,
    b => b.MigrationsAssembly("Services.Data.EF")));

services.AddTransient<Func<IMyDataContext>, Func<MyDataContext>>();
services.AddTransient(provider => new Func<IMyDataContext>(() => provider.GetService<IMyDataContext>()));

Then in my controller I have the following;

private ClientService _service;

public ClientController(Func<IMyDataContext> context)
{
    _service = new ClientService(context);
}

and the method in my service is;

private readonly Func<IMyDataContext> _contextFactory;

public ClientService(Func<IMyDataContext> contextFactory)
{
    _contextFactory = contextFactory;
}

public void AddClient(Client model, string userName)
{
    Func<Client> func = delegate
    {
        using (var context = _contextFactory())
        {
             ....
        }
    };

    return this.Execute(func);
}

Now from debugging if I inspect the controller injection I can see the Func is passed in and is at the service level 2. However when it comes to use it in the using statement on context = _contextFactory() it becomes null?

Any ideas what I am doing wrong here please?

Just for clarification. is context == null or _contextFactory == null ? — Alex
– Alex, Commented Mar 15, 2018 at 13:19
I'm not sure why you use Func<...> for your DataContext but I would assume your function does not generate a context. — Alex
– Alex, Commented Mar 15, 2018 at 13:47

Simply Ged · Accepted Answer · 2018-03-15 13:54:27Z

1

Your definitions are slightly wrong. You need to define that IDataContext and DataContext are related:

services.AddTransient<IDataContext, DataContext>();

Now the DI knows how to create the IDataContext. Now you method just needs to use the service provider to create it when the func is used:

services.AddTransient<Func<IMyDataContext>>(provider => () 
        => provider.GetService<IMyDataContext>());

Now, when your service is created, the DI will inject your Func<>

edited Mar 15, 2018 at 13:54

answered Mar 15, 2018 at 13:46

Simply Ged

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