我必须将查询从遗留数据库转换为LINQ，但我遇到了一些问题。基本上我需要做一个左连接，我想比较的属性是第二个表中属性的组合。

SELECT A.DATE, B.UNIT, B.PERSON
FROM TABLE1 A 
LEFT JOIN TABLE2 B ON A.KEY = CONCAT(B.UNIT, B.CONTRACT, B.VARIABLE)
WHERE B.DATE = someDate

字符串
到目前为止，我已经尝试过这种方式，但没有成功：

var date = someDate;

from a in _context.Table1

join b0 in _context.Table2 on a.Key equals $"{b0.Unit}{b0.Contract}{b0.Variable}" into bGroup
from b in bGroup.DefaultIfEmpty()
where b.Date == date
                    
select new ResponseDto
{
    Date = a.Date,
    Unit = b.Unit,
    Person = b.Person
})

{
  "Message": "The LINQ expression '...' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.",
  "ErrorName": "InvalidOperationException"
}

当删除字符串插值时，查询运行没有任何问题，所以我认为问题在于我处理这个问题的方式。有办法做到这一点吗？