简单的注入器如何将批处理注册的泛型类型注入构造函数

Question

Simple Injector newbie.

I've reviewed this documentation https://simpleinjector.readthedocs.io/en/latest/advanced.html to learn about how to work with generic types with simple injector.

I can't find in the documentation how to inject a class based on a generic type batch registration.

Here the documentation gives this example:

container.Register<IValidator<Customer>, CustomerValidator>();
container.Register<IValidator<Employee>, EmployeeValidator>();
container.Register<IValidator<Order>, OrderValidator>();
container.Register<IValidator<Product>, ProductValidator>();

can be registered like

container.Register(typeof(IValidator<>), typeof(IValidator<>).Assembly);

But what datatype do you use in the constructor so that simple injector injects the right concrete datatype.

For example

public classaconstructor(IValidator<Order> vdator)
{
}

I was trying to find the right getinstance method from the documentation, but could not find it. Thx.

Answer 1

The batch registration API you're referring to, is just a function which scans the assembly for all closed implementations of IValidator<T> .

So assuming IValidator<> actually lives in the same assembly as OrderValidator , this call

container.Register(typeof(IValidator<>), typeof(IValidator<>).Assembly);

will result in at least creating this registration:

container.Register<IValidator<Order>, OrderValidator>();

Which means that this simple unittest should pass:

[TestMethod]
public void RegisterIValidator_GetOrderValidatorInstanceSucceeds()
{
    var container = new Container();

    container.Register(typeof(IValidator<>),  typeof(IValidator<>).Assembly);

    container.Verify();

    var orderValidator = container.GetInstance<IValidator<Order>>();

    Assert.IsInstanceOfType(orderValidator, typeof(OrderValidator));
}

Now when you want to use OrderValidator in some other class, you indeed ask for IValidator<Order> in the constructor as you did. That is the whole point of dependency injection and programming to abstractions.

Simple Injector will never silently fail or inject null . So if injections fails, there will be descriptive exception (with possible inner exceptions) telling you where to look.

My best guess, with the information provided, is that OrderValidator is living in another assembly. Notice that this overload does accept multiple assemblies.

If this is not the case, post the stacktrace, with inner exceptions as well.