如何使用基于 SQL 查询的连接在 C# 中编写 LINQ？

Question

I need to write a linq based on the following query.

IN SQL Server,

select EXID,ID,NAME 
from Table1 A
join Table2 B on A.BXID = B.BID
left outer join Table3 C ON C.AXID = A.ID
AND C.EXID = (some number/NULL)

This gives me 300 records

In LINQ,

try
        {
            using (var context = new cltransformationContext())
            {
                var Details = (
                            from A in context.Table1
                            join B in context.Table2 on A.BXID equals B.BID
                            join C in context.Table3 on A.ID equals C.AXID  
                select new Table1()
                           {
                            ID = A.ID,
                            name = A.NAME + '-' B.Name
                            }).ToList();
                return Details;
            }
        }

I am getting 5000 records here.

I have missed left outer join and C.EXID = (some number/NULL) condition. How to do that in the query?

I should only get the 300 records.

Answer 1

This query will create LEFT JOIN:

var query =
    from A in context.Table1
    join B in context.Table2 on A.BXID equals B.BID
    from C in context.Table3.Where(C => A.ID == C.AXID && C.EXID == ...).DefaultIfEmpty()
    select new Table1
    {
        ID = A.ID,
        name = A.NAME + '-' B.Name
    };

Answer 2

This should do it

var query =
    from A in context.Table1
    join B in context.Table2 on A.BXID equals B.BID
    join table3 in context.Table3.Where(X => x.EXID = 123) on A.ID == table3.AXID into table3Joined
    from C in table3Joined.DefaultIfEmpty() // this is how we do the left join
    select new Table1
    {
        ID = A.ID,
        name = A.NAME + '-' B.Name
    };

The complexity lies in the fact that we have to place the join into table3Joined and then we can do from C in table3Joined.DefaultIfEmpty()