为什么需要IEnumerable<T>转成List<T>
这其实涉及到C#的两个问题：
- 引用对象的赋值是不是如你所预期；
- 为什么需要IEnumerable
转成List
不看结果，先看代码：
'''C#
var indexArray = new int[]{1,2,3,4,5,6 };
var members = indexArray.Select (i => new Member{ Index = i });
Console.WriteLine ("Case 1");
var member1 = members.FirstOrDefault (m => m.Index == 1);
var member1_C = member1;
var member1_W = members.FirstOrDefault (m => m.Index == 1);
member1.Name = "Yang SHEN (Case 1)";
Console.WriteLine (member1.Equals(member1_W));
Console.WriteLine (member1.Equals(member1_C));
Console.WriteLine (member1_W.Name);
Console.WriteLine (member1_C.Name);
Console.WriteLine ("Case 2");
var memberList = members.ToList ();
var member1inList = memberList.FirstOrDefault (m => m.Index == 1);
var member1inList_W = memberList.FirstOrDefault (m => m.Index == 1);
member1inList.Name = "Yang SHEN (Case 2)";
Console.WriteLine (member1inList.Equals(member1inList_W));
Console.WriteLine (member1inList_W.Name);
Console.WriteLine ("Case 3");
var member2 = memberList[memberList.FindIndex(m=>m.Index ==2)];
var member2_W = memberList[memberList.FindIndex(m=>m.Index ==2)];
member2.Name = "Yang SHEN (Case 3)";
Console.WriteLine (member2.Equals(member2_W));
Console.WriteLine (member2_W.Name);
'''
不看运行结果，目测一下各个Console.WriteLine的输出是什么？？
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有意思，同样通过 FirstOrDefault 获得一个集合中的对象，不过，IEnumerable
