求一个linq或lambda的联合查询

[fayxue]

表1
userid,name
1，张三
2，李四
3，王五

表2
userid,date,state
1，2018-01-01，在
1，2018-01-02，在

查询2018-01-01所有人的状态的结果
1，张三，2018-01-01，在
2，李四，2018-01-01，null
3，王五，2018-01-01，null

[peng2739956]

void Main()
{
	List<student> list=new List<student>(){new student{userid=1,name="张三"},new student{userid=2,name="李四"},new student{userid=3,name="王五"}};
	List<dateState> list1=new List<dateState>(){new dateState{userid=1,data="2018-01-01",state="在"},new dateState{userid=1,data="2018-01-02",state="在"}};
    var result = from l in list
                         join p in list1.DefaultIfEmpty(new dateState()) on l.userid equals p.userid into m						 
                         select new { userid = l.userid, name = l.name,data=m.Min(t=>t.data), state = m.Where(t => t.userid == l.userid).Select(t => t.state).FirstOrDefault() };
						 result.Dump();
}
class student
{
	public int userid{get;set;}
	
	public string name{get;set;}
}
class dateState
{
	public int userid{get;set;}
	
	public string data{get;set;}
	
	public string state{get;set;}
}

[青稞一梦]

class student
{
    public int userid{get;set;}
     
    public string name{get;set;}
}
class dateState
{
    public int userid{get;set;}
     
    public string data{get;set;}
     
    public string state{get;set;}
}
public IQueryable<dynamic> GetAll() 
        {
            var ss = db.Set<student>()
                .Join(db.dateState, p => p.userid, c => c.userid, (p, c) => new { p.userid, p.name, c.data,c. state})
                .Distinct();
        }

[fifexue]

DefaultIfEmpty() 左连接