实体框架中连接子句中的表达式之一的类型不正确 [英] The type of one of the expressions in the join clause is incorrect in Entity Framework

问题描述

尝试执行此查询时:

var query = from dpr in ctx.DPR_MM
            join q in ctx.QOT on dpr.DPR_QOT_ID equals qot_id
            join p in ctx.PAY_MM on new { q.QOT_SEC_ID, dpr.DPR_TS } equals new { p.PAY_SEC_ID, p.PAY_DATE }
            where q.QOT_ID = qot_id
            select new
            {
                dpr.dpr_ts,
                dpr.dpr_close,
                pay.First().pay_dividend
            };

我收到此错误:

join 子句中的表达式之一的类型不正确.调用加入"时类型推断失败.

The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.

QOT_SEC_ID 是 decimal 类型，PAY_SEC_ID 是 int32 类型.我不允许在表格中更改它.

QOT_SEC_ID is of type decimal and PAY_SEC_ID is of type int32. I'm not allowed to change it in the table.

无论我做什么，我都无法在模型的属性中更改它.我试图转换这样的类型:

No matter what I do, I'm not able to change it in model's properties. I have tried to convert the types like this:

join p in ctx.PAY on new { sec_id = (Int32)(q.QOT_SEC_ID), dpr.DPR_TS } equals new { sec_id = (Int32)p.PAY_SEC_ID, p.PAY_DATE }

但得到上面的错误.

推荐答案

匿名类型中的类型和属性名称必须匹配:

The types and the names of the properties in the anonymous types must match:

new { p1 = q.QOT_SEC_ID, p2 = dpr.DPR_TS } 
    equals 
new { p1 = (decimal)p.PAY_SEC_ID, p2 = p.PAY_DATE }

或者如果 p.PAY_SEC_ID 是 int?:

new { p1 = (int?)q.QOT_SEC_ID, p2 = dpr.DPR_TS } 
    equals 
new { p1 = p.PAY_SEC_ID, p2 = p.PAY_DATE }

...将找不到匹配项 PAY_SEC_ID 是 null，或者

...which will find no matches PAY_SEC_ID is null, or

new { p1 = q.QOT_SEC_ID, p2 = dpr.DPR_TS } 
    equals 
new { p1 = p.PAY_SEC_ID.GetValueOrDefault(), p2 = p.PAY_DATE }

...当 PAY_SEC_ID 为 null 时，默认 p1 为 0 并且再次找不到匹配项(假设 ID 值永远不会是 0).

...which defaults p1 to 0 when PAY_SEC_ID is null and again no match will be found (assuming that ID values will never be 0).

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