Linq Zip combined with AutoMapper-CodePudding

I have a loop which uses AutoMapper to map two different instances of objects A & B into a new instance of a third object, C. The object C contains all the fields of A & B combined.

In other words, they could look like this:

class A
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

class B
{
    public DateTime TimeOfBirth { get; set; }
}

// A & B combined
class C
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime TimeOfBirth { get; set; }
}

Currently I have a loop which uses AutoMapper to first map A into C. And then map B into the result. Like this:

List<C> output = new();

foreach (var a in listA)
{
    C result = _mapper.Map<C>(a);

    _mapper.Map<B, C>(listB.Single(b => b.Id == a.ForeinKey), result);

    output.Add(result);
}

I would like to do this with Linq. My initial thought was to use the Zip method, but I cannot get it to work with AutoMapper. I would expect that it should look something like the below, but I cannot get it to work (it doesn't compile):

var output = _mapper.Map<C>(listA).Zip(_mapper.Map<C>(listB));

What am I missing? Is it even possible to do what I am trying - without making an even bigger mess?

CodePudding user response：

Since you want to do an in-place mapping the second time, you still need to call Map<B, C>(b, existingC). For that you can use the Zip overload taking a selector fucntion:

var output = _mapper.Map<C>(listA)
    .Zip(listB, (c, b) => _mapper.Map<B, C>(b, c));

CodePudding user response：

You have to use Join in such case:

var output = listA
    .Join(listB, a => a.ForeinKey, b => b.Id, (a, b) => 
       _mapper.Map<B, C>(_mapper.Map<C>(a))
    )
    .ToList();