Question

概述

这是在Visual Basic应用程序中使用LINQ to SQL的家庭作业。除了我有一个部分破碎的结果外，它在大多数方面都是正确的。我的代码不是将我的第二个查询的结果添加到我的列表框中，而是添加了查询本身的奇怪表示。下面是DB的描述，后面是我的输出（预期和实际），最后是我的代码。请指出我破碎的概念，这样我就可以弄清楚我错过了什么。非常感谢。

数据库信息

我在一个数据库中使用两个名为Members and Payments的表。成员有一个名为ID的主键，还有字段first_name和last_name。付款有一个名为Members_Id的外键，它与会员的主键相关联;付款还包含Payments列下的付款值。

输出应该是这样的

Member name = John Smith
    $48.00,  10/20/2005
    $44.00,  3/11/2006

但是这是

Member name = SELECT ([t0].[First_Name] + @p1) + [t0].[Last_Name]
              AS [value]FROM[dbo].[Members] AS [t0].[ID] = @p0

    $48.00,  10/20/2005
    $44.00,  3/11/2006

我的VB代码

Public Class FormPaymentsGroup
    Private db As New KarateClassesDataContext

Private Sub FormPaymentsGroup_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    Me.PaymentsTableAdapter.Fill(Me.KarateDataSet.Payments)

    'Group payments by Member_ID (FKey) in the Payments table. (Working fine)
    Dim IdQuery = From aMember In db.Payments
                Group aMember By aMember.Member_Id
                Into MemberPayments = Group

    For Each memberID In IdQuery
    ' Use the passed member_Id to target the row in the Members table and return the first_name & last_name.
    ' PROBLEM: This only seems to be returning the query itself; not the result.
        Dim currMemberID = memberID.Member_Id
        Dim nameQuery = From aName In db.Members
                        Where aName.ID = currMemberID
                        Select aName.First_Name + " " + aName.Last_Name

        Dim currName = nameQuery.ToString ' Load the query result into a portable variable.

        LbxMemberPayments.Items.Add("Member name = " & currName) ' PROBLEM: This is where the name SHOULD BE posted to the listbox.

        ' This is bound to the Members table but directs it based on the above IdQuery.
        For Each enteredPayment In memberID.MemberPayments
            LbxMemberPayments.Items.Add(vbTab & FormatCurrency(enteredPayment.Amount) & ",  " & enteredPayment.Payment_Date)
        Next
        LbxMemberPayments.Items.Add(vbCr)   ' Carriage return formatting
    Next

End Sub
End Class

Answer 1

更改

   Dim currName = nameQuery.ToString

到

    Dim currName = nameQuery.FirstOrDefault

LINQ to SQL，Visual Basic - Listbox接收查询而非结果

概述

数据库信息

我的VB代码

1 个答案: