使用Linq的First找到数组中的一条记录，能否得到它在数组中的索引号？

[中文命名法]

数组[0]="a";;
数组[1]="b";
数组[2]="c";
数组[3]="d";
数组[4]="e";
var 目标=数组.First(f=>f=="c");

然后能得到它的索引号吗？也就是2

[正怒月神]

static List<User> list = new List<User>()
        {
            new User(){id=1,name="1"},
            new User(){id=2,name="2"},
            new User(){id=3,name="3"},
            new User(){id=4,name="4"},
            new User(){id=5,name="5"},
            new User(){id=6,name="6"},
            new User(){id=7,name="7"},
            new User(){id=8,name="8"},
        };

        
        public class User
        {
            public int? id { get; set; }
            public virtual string name { get; set; }
            public virtual string add { get; set; }
            public User MyClone()
            {
                return (User)this.MemberwiseClone();
            }
        }
        
        static void Main(string[] args)
        {
            //转换为数组
            var q = list.ToArray();

            var v = q.Select((x, i) => new
            {
                user = x,
                i
            }).First(x => x.user.id == 3);

            Console.WriteLine(v.i);

            Console.ReadLine();
        }

[正怒月神]

或者，你可以直接找下标，而不需要返回的对象 var q = list.FindIndex(x => x.id == 3); Console.WriteLine(q);

[q107770540]

what if you have duplicate value?

void Main()
{
	 List<User> list = new List<User>()
		{
			new User(){id=1,name="1"},
			new User(){id=2,name="2"},
			new User(){id=3,name="3"},
			new User(){id=4,name="4"},
			new User(){id=5,name="5"},
			new User(){id=6,name="6"},
			new User(){id=7,name="7"},
			new User(){id=8,name="8"},
			new User(){id=9,name="6"}
		};
 
	string name = "6";
	
	var query = list.Select((value,index)=>	new {Index = index, Value = value})
					.Where(user=>user.Value.name==name)
					.Select(user=>user.Index)
					.ToArray();
 
}
public class User
		{
			public int? id { get; set; }
			public virtual string name { get; set; }
			public virtual string add { get; set; }
			public User MyClone()
			{
				return (User)this.MemberwiseClone();
			}
		}