查询Linq返回列表 <int> 从对象

Question

I have this class :

public class MyClass
{
    public int Id { get; set; }
    public int MyId1 { get; set; }
    public int MyId2 { get; set; }
    public int MyId3 { get; set; }
    public string MyName { get; set; }
}

I have a List<MyClass>

I do a query :

var result = (from my in MyClass
             where Id == 5
             select my).First();

I'd like in result a List with MyId1, MyId2 and MyId3

Any idea ?

Thanks,

Answer 1

var result = (from my in list
             where my.Id == 5
             select new List<int>() { my.MyId1, my.MyId2, my.MyId3 }).First();

Answer 2

I think there is two steps in your code: (1) obtaining required object and (2) convert that object to list. So actually I think more appropriate would be something like this:

var firstResult = list.First(my => my.Id == 5);
var result = new List<int>{firstResult.MyId1, my.MyId2, my.MyId3};

This approach is more slightly better because it simpler and states you intention more clear.

Consider Single Responsibility Principle : your code should have only one reason to change. Your code (and Arsen's code as well) lacks of this ability. When requirements changed and you'll need to change your class or add additional property to the list you'll need to change your filtering logic. But its clear that those two aspects are orthogonal and should not changed in such circumstances.

BTW you can add extension method or simple method to your class MyClass that will convert it to List. In this case your code would be even more readable:

var result = list.First(my => my.Id == 5).ToListOfInt();