Passing function as parameter in c# works but not in vb.net?

Question

So I have the following line of code in c# to register AutoMapper with SimpleInjector:

container.Register(() => config.CreateMapper(container.GetInstance));

For context, config.CreateMapper() looks like this:

public IMapper CreateMapper(Func<Type, object> serviceCtor);

While container.GetInstance looks like this:

public object GetInstance(Type serviceType);

The first line of code I posted works in C# because config.CreateMapper takes in a function that takes a type of Type and returns a type of object. Exactly what container.GetInstance does.

When I try to do this same line in VB, as:

container.Register(Function() config.CreateMapper(container.GetInstance))

It gives an error Type arguments for 'Public Function Container.GetInstance(Of TService)()' cannot be inferred from the usage. Try specifying type arguments explicitly. It is giving this error because container.GetInstance has an overload that looks like this:

public TService GetInstance<TService>() where TService : class;

Why does the VB try to use the wrong overload of GetInstance and how can I force it to use the correct one?

() are optional, right now it's trying to call the method GetInstance without any parameters. — the_lotus
– the_lotus, Commented Jul 6, 2017 at 16:57

Fabio · Accepted Answer · 2017-07-06 17:02:04Z

1

Use AddressOf for getting function reference.

container.Register(Function() config.CreateMapper(AddressOf container.GetInstance))

In C# function with parenthesis executes it, function without parenthesis will return reference to the function.

In VB.NET parenthesis in function are optional - function will be executed anyway. So for referencing a function you should use AddressOf operator.
AddressOf Operator

edited Jul 6, 2017 at 17:02

answered Jul 6, 2017 at 16:53

Fabio

32.5k4 gold badges35 silver badges77 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jun Kang Over a year ago

Thank you! Learn something new everyday.

Toni Wenzel · Accepted Answer · 2017-07-06 17:00:59Z

0

Use the AddressOf keyword before the function parameter to define this as Parameter as function pointer.

AddressOf ist the same as @ keyword in C#. The keyword is implicit used in your c# sample.

answered Jul 6, 2017 at 17:00

Toni Wenzel

2,0913 gold badges24 silver badges41 bronze badges

Collectives™ on Stack Overflow

Passing function as parameter in c# works but not in vb.net?

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related