c# - using linq with join using two where on two tables

Question

I am using Csharp Linq to create the following report

I have two tables as below

#Users
nid     pid     name
1       1       name1
2       1       name2

#Transactions
nid     tid     location    dcode 
1       T1      L1          D1
2       T1      L2          D1
2       T2      L1          D1
2       T2      L3          D1

The report contains

    a) columns from users table where nid != pid
    b) columns from transactions where tid == T2 and nid = results from a)
    c) the combination can have only one top row  in result 

nid     name        tid     Location
2       name2       T2      L1

the second record will not be present
- 2     name2       T2      L3

I have tried the following, using join

var report = (from u in users where u.nid != u.pid
                      join t in transactions
                      where t.tid == "T2"
                      on u.nid equals t.nid
                      select new 
                      {
                        // the report columns
                      }).Distinct().ToList();

on the second 'where' a Error is displayed

thank you for any assistance

Answer 1

交换过滤和连接部分查询并重命名tid为t.tid或其他所需的过滤子句（在您的示例中，结果表确实有事务tid == "T1"，但您尝试使用 过滤T2）：

var report = (from u in users     
              join t in transactions 
              on u.nid equals t.tid     //<-- this line should precede 
              where t.tid == "T2"       //<-- this one
              && u.nid != u.pid
              select new 
              {
                    // the report columns
              }).Distinct().ToList();

连接部分不能分开，所以where在你完成joinwithon子句之前你不能写。