将列表从一个类转换为另一个类

我正在尝试将组转换为C#(使用Linq)中的复杂列表

public class classA    
{    
    public string Name { get; set; }    
    public int id { get; set; }    
    public string phone { get; set; }    
    public string interest { get; set; }    
}

classA 其中包含许多元素列表,如下所示。

List<classA> obj = new List<classA>();
obj.Add(new classA { id = 1, Name = "a", phone = "321", interest = "Playing" });    
obj.Add(new classA { id = 1, Name = "2", phone = "123", interest="Tv" });

从这里我需要使用id来分组,所以我使用 Linq

 var item = obj.GroupBy(a => a.id).Select(ac => ac.ToList()).ToList();

我还有一门课叫 classB 其中包含了 甲级

public class classB
{
    public string Name { get; set; }
    public string phone { get; set; }
    public string interest { get; set; }
}

我的最后一堂课看起来像,

public class Final
{
    public int id { get; set; }
    public List<classB> details { get; set; }

    public Final()
    {
        details = new List<classB>();
    }
}

我的要求是,分组后 基于 id ,我需要把它转换成我的 final 班级。

所以我喜欢下面的内容,

public static void Main()
{
    Console.WriteLine("Hello World");
    List<classA> obj = new List<classA>();
    obj.Add(new classA { id = 1, Name = "a", phone = "321", interest = "Playing" });
    obj.Add(new classA { id = 1, Name = "b", phone = "123", interest = "Tv" });
    obj.Add(new classA { id = 2, Name = "c", phone = "12322", interest = "Tv" });
    obj.Add(new classA { id = 3, Name = "d", phone = "12333", interest = "Tv" });

    var item = obj.GroupBy(a => a.id).Select(ac => ac.ToList()).ToList();
    List<Final> finalobjList = new List<Final>();

    foreach (var report in item)
    {

        Final finalObj = new Final();
        foreach (var result in report)
        {
            finalObj.id = result.id;
        }

        var data = report.Select(x => new classB { Name = x.Name, phone = x.phone, interest = x.interest }).ToList();
        finalObj.details = data;
        finalobjList.Add(finalObj);

    }

    Console.WriteLine(finalobjList.Count());
}

我相信有另一个简单的方法来实现这一点 linq 不使用 foreach

谢谢你的帮助!