选择类型查询以使用Linq将其转换为其子类型

Question

I am working on a ASP.Net core project, and i have a model as below :

Class abcde
{
   int a {get;set;}
   int b {get;set;}
   int c {get;set;}
   int d {get;set;}
   int d {get;set;}
}

In a particular view i just required properties a and b of the above defined model. So, i just define a ViewModel class (into a different namespace) as below :

Class ab
{
   int a {get;set;}
   int b {get;set;}
}

Now in the controller i am making a select query, and i intend to select only a and b properties. As these are the only properties i want to show in the view. So, basically my query must be :

var objects = _context.abcde.Select( x=> new {x.a, x.b}).ToArray()

The problem here is that i get a Array of an anonymous type, which i need to map manually to my viewmodel class ab. In this case, i will have to have a loop to manually transform each of the result-set into the ViewModel.

Looking at the signature of Select function

Enumerable.Select TSource, TResult

It appears, that the function itself can do the transformation, but i couldn't find any examples. I might be having a wrong thought here. Can you please suggest the way to handle such a scenario. I believe this is going to be very common case. Thanks in advance.

Answer 1

The problem here is that i get a Array of an anonymous type, which i need to map manually to my viewmodel class ab. In this case, i will have to have a loop to manually transform each of the result-set into the ViewModel.

So just project using the ab class by using it like this:

x => new ab() { a = x.a, b = x.b }

Instead of using anonymous type:

x => new { x.a, x.b }

So your final query will look like below:

var objects = _context.abcde.Select(x => new ab { a = x.a, b = x.b }).ToArray()