Injection Constructor Dependency Injection with parameters

Question

I am trying to understand how do I resolve multiple parameters being passed to a constructor from a DI container.

I have an interface IDataAccess (#1) and a class called SQL implementing IDataAccess (#2). Another class ObjectBroker (#3) that supplies the Instance of any concrete class that implements interface. I am using unity container for constructor dependency injection as shown in (#4).

All this works well, until I try to add more parameters to the ObjectBorker constructor. For example if I do this --> public ObjectBroker(IDataAccess da, string s), then I am not able to understand how do I resolve the parameters for the DI container?

 //region #1 
 public interface IDataAccess
 {
 string GetDataBaseName();
 }
 //endregion
 //region #2 
 public class SQL : IDataAccess 
 {
 public string GetDataBaseName()
 {
 return "Data retrieved from SQL, Microsoft";
 }
 }
 //endregion
 //region #3 
 public class ObjectBroker 
 {
 private IDataAccess dataAccess;
 
 public ObjectBroker(IDataAccess da) //Fails if I have public ObjectBroker(IDataAccess da, string s)
 {
 dataAccess = da;
 }
 public string GetDataBaseName()
 {
 return dataAccess.GetDataBaseName();
 }
 }
 //endregion
 //region #4 
 IUnityContainer iuContainer3 = new UnityContainer(); 
 iuContainer3.RegisterType<IDataAccess, SQL>("SQL");
 var con = new InjectionConstructor(iuContainer3.Resolve<IDataAccess>("SQL"));
 iuContainer3.RegisterType<BusinessFactory>("SQL", con);
 //endregion

Tried this var con = new InjectionConstructor(iuContainer3.Resolve(new ResolverOverride[] { new ParameterOverride("da", "SQL"), new ParameterOverride("s", "PSQL") }));

But getting an error Unity.ResolutionFailedException: 'Resolution failed with error: No public constructor is available for type DependencyInjection.IDataAccess

Answer 1

Solution using InjectionConstructor:

var con = new InjectionConstructor(iuContainer3.Resolve<IDataAccess>("SQL"), "PSQL");
iuContainer3.RegisterType<ObjectBroker>("SQL", con);

InjectionConstructor instantiated with two parameters:

• iuContainer3.Resolve<IDataAccess>("SQL") which will be mapped to da constructor parameter.
• PSQL which will be mapped to s constructor parameter.

Here is an interactive full example.

Solution using InjectionFactory:

iuContainer3.RegisterType<ObjectBroker>("SQL", new InjectionFactory(CreateDataAccessLayer));
private static IDataAccess CreateDataBaseLayer(IUnityContainer container)
{
 var da = container.Resolve<IDataAccess>();
 return new ObjectBroker(da, "PSQL");
}

• Prasanth Sarath: Sorry if I was not clear, my goal is to achieve something like this...ObjectBroker bSQL3 = iuContainer3.Resolve<ObjectBroker>("SQL"); Console.WriteLine($"Requested company name is {bSQL3.GetDataBaseName()}"); so that it prints the output. But when I use your first solution I am not able to resolve and I still get the same runtime error
• Vadim Martynov: @PrasanthSarath well I can't reproduce your behavior. It works fine inside the repl: replit.com/@VadimMartynov/…
• Prasanth Sarath: Fantastic! I saw the Interactive example and it worked like a charm. Wonderful, thanks for not only solving my problem but you have given the interactive example that helped me a lot, thank you so much