该类型前pressions之一的诠释，他的加盟条款不正确。类型推断在调用'加盟'失败 [英] The type of one of the expressions int he join clause is incorrect. Type inference failed in the call to 'join'

问题描述

目前，我正在试图加入另一个表中的列到现有的表，并将其返回到MVC 4

I'm currently trying to join a column from another table to an existing table and return it to the view in MVC 4

var q = from accCo in db.AccControls
        join accCom in db.AccCompanies
        on new { accCo.ControlCode } equals
        new { ControlCode = accCom.Code }

        where accCo.ControlCode == Request.QueryString["ControlCode"]
        orderby accCom.Code
        select new Combined{ AccControls = accCo, AccCompoanies = accCom };

return View(q);

但我发现了上面的错误

But I'm getting the above error

推荐答案

如果你任何关于加盟列可为空，则需要将其更改为.value的

If any of the columns you join on is nullable, you will need to change it to .Value

on new { accCo.ControlCode } equals
            new { ControlCode = accCom.Code.Value }

或者您可以使用此

or you can use this

var q = from accCo in db.AccControls
    join accCom in db.AccCompanies
    where accCom.Code != null
    on new { accCo.ControlCode } equals
    new { ControlCode = accCom.Code }

    where accCo.ControlCode == Request.QueryString["ControlCode"]
    orderby accCom.Code
    select new Combined{ AccControls = accCo, AccCompoanies = accCom };

这篇关于该类型前pressions之一的诠释，他的加盟条款不正确。类型推断在调用'加盟'失败的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！