linq 连接表错误

Question

加入表格时出现错误，将结果作为列表返回。这是我的代码。请帮忙。谢谢

Public Function GetMerchantList() As List(Of Merchant)
        Dim Db As New TTMSEntities

        Dim Data = From p In Db.TT_MERCHANT Join r In Db.TT_BRANCH_SETTING On _
                   p.MERCHANT_BRANCH_INTERNAL_NUM Equals r.INTERNAL_NUM
                   Select New With {p.MERCHANT_ID, p.DESCRIPTION, r.INTERNAL_NUM, r.BRANCH_DESC}

        If Data IsNot Nothing Then
            Return ConvertMerchant(Data)
        Else
            Return Nothing
        End If
    End Function

错误 无法将“System.Data.Entity.Infrastructure.DbQuery1[VB$AnonymousType_04[System.String,System.String,System.Decimal,System.String]]”类型的对象转换为“System.Collections.Generic.List”类型1[TTMS.App.WebSites.Data.Merchant]

Answer 1

您的 Data 变量具有匿名类型的 IQueryable 类型，因此您需要指定您想要的类型并调用 ToList 类似的东西

Public Function GetMerchantList() As List(Of Merchant)
    Dim Db As New TTMSEntities

    Dim Data = (From p In Db.TT_MERCHANT Join r In Db.TT_BRANCH_SETTING On _
               p.MERCHANT_BRANCH_INTERNAL_NUM Equals r.INTERNAL_NUM
               Select New Merchant With {p.MERCHANT_ID, p.DESCRIPTION, r.INTERNAL_NUM, r.BRANCH_DESC}).ToList()

    If Data IsNot Nothing Then
        Return ConvertMerchant(Data)
    Else
        Return Nothing
    End If
End Function

还有Data 总是不为空（或者对于 VB 为空）它可以为空