Linq的左链接

地址：https://docs.microsoft.com/en-us/dotnet/csharp/linq/perform-left-outer-joins

①创建两张表和一些基础数据做我们的测试

②我们的 查询语句

 [HttpGet]
        public async Task<IHttpActionResult> Init()
        {
            var linq = from a in db.JoinAs
                       join b in db.JoinBs on a.ACode equals b.ACode into gj
                       from ee in gj.DefaultIfEmpty()
                       select new
                       {
                           AName = a.AName,
                           ACode = a.ACode,
                           BName = ee.BName ?? ""
                       };
            return await Task.FromResult(Ok(new { data = linq }));
        }

查询结果：

③ 查看我们的Linq翻译的sql语句，LinqPad