Unity InjectionConstructor Passing Object array

Question

I am trying to register dependency using unity and pass values to constructor,using the code below

container.RegisterType<IProviderContext, MockOrderServiceProviderContext>(new InjectionConstructor(new Pharmacy {SiteId = 2,DistrictCode = "2"}));

but I am getting

"The type OrderService.Business.MockOrderServiceProviderContext does not have a constructor that takes the parameters (Pharmacy)."

Constructor.

public MockOrderServiceProviderContext(params object[] objects)
     {
         _object = objects;
     }

How do you pass constructor values for object array ?

Thanks

Lukazoid · Accepted Answer · 2013-02-28 23:24:45Z

5

The params keyword is syntactic sugar for passing an array of arguments.

The following method:

public void MyMethod(params object[] args)
{
}

Can be invoked in both of the following ways with the same results:

MyMethod(new object(), new object());
MyMethod(new []{ new object(), new object());

When Unity looks for constructors, it sees a constructor with one parameter of type object[]. So the value provided by Unity must be an array.

The InjectionConstructor also utilises the params keyword, where each parameter is a value to forward to your own constructor. If you instantiate the InjectionConstructor with an array, it will try and use each element of the array and forward them to your class constructor.

To stop this, we require two levels of wrapping, one for unity to provide an array to your class, and one so that the InjectionConstructor uses the first array as the first and only parameter.

So you should use the following:

container.RegisterType<IProviderContext, MockOrderServiceProviderContext>(
    new InjectionConstructor(new []
    {
       new []
       {
           new Pharmacy { SiteId = 2, DistrictCode = "2" }
       }
    }));

If you want additional items to be passed, merely add them to the inner array:

container.RegisterType<IProviderContext, MockOrderServiceProviderContext>(
    new InjectionConstructor(new []
    {
       new []
       {
           new Pharmacy { SiteId = 2, DistrictCode = "2" },
           new Hospital { SiteId = 5, DistrictCode="2" }
       }
    }));

edited Feb 28, 2013 at 23:24

answered Feb 28, 2013 at 22:29

Lukazoid

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3 Comments

JoR Over a year ago

thanks for the explanation about params and injectionconstructor

Lukazoid Over a year ago

@JoR No problem, I hope it made sense.

brazilianldsjaguar Over a year ago

Very helpful explanation, even 3 years later!

Lukazoid · Accepted Answer · 2013-02-28 23:27:55Z

2

This is how I got it working.

You have to add objects to an array and then add them to a container array so that it matches with the constructor parameter signature

var objAr = new object[2];
objAr[0] = new Pharmacy { SiteId = 3, DistrictCode = "2" };
objAr[1] = new Facility { SiteID = 1, FacilityCode="Facility" };

//Add the object array to another container array so that Unity Injection constructor can match the constructor.
var containerArray = new object[1];
containerArray[0] = objAr;

container.RegisterType<IProviderContext, MockOrderServiceProviderContext>(new InjectionConstructor(containerArray));

edited Feb 28, 2013 at 23:27

Lukazoid

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answered Feb 27, 2013 at 16:40

JoR

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Comments

Joetjah · Accepted Answer · 2013-02-27 15:36:53Z

-1

Correct me if I'm wrong, but aren't you trying to give a paramater with your MockOrderServiceProviderContext which isn't an array?

You give new InjectionConstructor(..) as a parameter instead, or object if you like to say so, instead of object[].

answered Feb 27, 2013 at 15:36

Joetjah

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2 Comments

JoR Over a year ago

Actually no. The idea of having object array is so that we can pass multiple objects. Like new InjectionConstructor(new Pharmacy {SiteId = 2,DistrictCode = "2"},new Hospital {ID =1,name="SSS"} Thanks

Lukazoid Over a year ago

@joetjah In the registration with Unity, the parameters to InjectionConstructor are used to determine the parameters when injecting the values. The InjectionConstructor is not actually used as a parameter value.

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