如何使用另一个列表执行列表的Linq查询

Question

I have a List of Member class, members. The Member class has the following properties:

MemberId : string MemberName : string DateOfBirth : DateTime

List<Member> members = FindMembers();

I have a separate List of MemberId, as shown below.

List<string> memberIds = GetTeenAgeMemberIds();

Now I have to query the Members list with the values in the memberIds List. Please let me know how could I do this using Linq.

Answer 1

You can use the following LINQ query:

var result = members.Where(m => memberIds.Contains(m.MemberId)).
    ToArray();

Alternatively:

var result = (from m in members
              join id in memberIds on m.MemberId equals id
              select m).ToArray();

Or if you prefer method chains:

var result = members.Join(memberIds, m => m.MemberId, id => id, (m, id) => m).
    ToArray();

Answer 2

使目标列表成为一个数组或明显托管的东西，使用Contains来比较你拥有的MemberId和你的列表。