How can I use the following AutoMapper generic method in VB.NET (without executing the method): Mapper.Map

Question

This is my first question here so please go easy on me ;-)

I am taking a course on Udemy to learn ASP.NET MVC 5. This course is being taught using C# but I have been following along using VB.NET. Right about half-way through the course, the instructor introduces a library called AutoMapper for mapping domain objects to DTOs (data transfer objects).

The C# code I am having trouble with:

return _context.Customers.ToList().Select(Mapper.Map<Customer, CustomerDto>);

In VB.NET I believe it should be:

Return _context.Customers.ToList().[Select](Mapper.Map(Of Customer, CustomerDto))

However I am receiving the following errors:

• Overload resolution failed because no accessible 'Map' accepts this number of arguments.

• Overload resolution failed because no accessible '[Select]' can be called with these arguments: Extension method 'Public Function [Select](Of TResult)(selector As Func(Of Customer, TResult)) As IEnumerable(Of TResult)' defined in 'Enumerable': Type parameter 'TResult' cannot be inferred.

The signature of the AutoMapper function being called:

VB.NET

Public Shared Function Map(Of TSource, TDestination)(source As TSource) As TDestination

C#

public static TDestination Map<TSource, TDestination>(TSource source);

It would appear that while C# allows omitting the (TSource source) parameter, VB.NET is requiring the same parameter (source As TSource)

Answer 1

The C# construct being used here is called a Method Group.

The construct without a method group in C# would be to use a lambda expression, like this:

list.Select(c => Mapper.Map<Customer,CustomerDto>(c))

Which translates to VB.Net as follows:

list.Select(Function(c) Mapper.Map(Of Customer, CustomerDto)(c))

You can achieve something similar to the C# method group in VB.Net with the AddressOf operator:

list.Select(AddressOf Mapper.Map(Of Customer, CustomerDto))