Question

我想要一个循环查询结果的代码，并将它们显示在visual basic的列表框中。到目前为止我所拥有的是存储过程，列表框和按钮。

存储过程即时调用被称为＆＃34; CycleCustomers＆＃34;并且sql for that如下：

 ALTER PROCEDURE CycleCustomers 
-- Add the parameters for the stored procedure here
@p1 int

  AS
  BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

-- Insert statements for procedure here
SELECT FirstName from tblCustomer where CustomerId = @p1
 END

点击按钮时的代码如下

 Dim dc = New DataTestDataContext
    Dim DealerCount As Int32
    DealerCount = 0
    ListBox2.Items.Clear()

    Do Until DealerCount = 10
        dc.CycleCustomers(DealerCount)
        ListBox2.Items.Add(dc.CycleCustomers(DealerCount).ReturnValue)
        DealerCount = DealerCount + 1
    Loop

单击该按钮时，我的列表框将返回10个零。我究竟做错了什么？提前致谢。

编辑：这是循环系统功能

 <FunctionAttribute(Name:="dbo.CycleCustomers")>  _
Public Function CycleCustomers(<Parameter(DbType:="Int")> ByVal p1 As System.Nullable(Of Integer)) As ISingleResult(Of CycleCustomersResult1)
    Dim result As IExecuteResult = Me.ExecuteMethodCall(Me, CType(MethodInfo.GetCurrentMethod,MethodInfo), p1)
    Return CType(result.ReturnValue,ISingleResult(Of CycleCustomersResult1))
End Function

Answer 1

看看这里：http://msdn.microsoft.com/en-us/library/bb534556(v=vs.110).aspx

你得到的是一个类型为CycleCustomerResult1的ISingleResult，它是一个IEnumerable。你应该用Linq做什么就像：

Dim dc = New DataTestDataContext
Dim DealerCount As Int32
DealerCount = 0
ListBox2.Items.Clear()

Do Until DealerCount = 10
  Dim Customer = dc.CycleCustomers(DealerCount).SingleOrDefault()

  If (Not(Customer Is Nothing))
    ListBox2.Items.Add(Customer.FirstName)
  End If

  DealerCount = DealerCount + 1

Loop

我目前没有Visual Studio来检查这个：我通常使用C＃，因此我的VB的精度可能很差。

但无论如何，你所采取的做法似乎非常不正统。理想情况下，您将拥有一个存储过程，该存储过程返回一组行，然后迭代遍历该结果，并在您执行此操作时添加到列表框中。

例如，像这样的存储过程：

ALTER PROCEDURE CycleCustomers 
  AS
  BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

-- Insert statements for procedure here
SELECT FirstName from tblCustomer 
 END

然后是一个更像这样的功能

Dim Customers = dc.CycleCustomers()

For Each Customer In Customers
  ListBox2.Items.Add(Customer.FirstName)
Next

Answer 2

好的，我是通过LINQ to SQL和存储过程完成的，但现在可以正常工作了。这是按钮的代码

 Dim number As Int32
    number = 1
    Dim dc = New DataTestDataContext

    Do Until number > dc.MaxCustomerId.First.CustomerId
        Dim Customers = From cust In dc.CycleCustomers(number) _
                      Where cust.CustomerId = number _
                      Select cust

        For Each cust In Customers
            ListBox2.Items.Add(cust.FirstName)

        Next
        number = number + 1
    Loop

这是存储过程代码

 ALTER PROCEDURE CycleCustomers 
-- Add the parameters for the stored procedure here
@p1 int

   AS
   BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

-- Insert statements for procedure here
SELECT CustomerId, FirstName from tblCustomer where CustomerId = @p1
 END

我为循环创建了另一个存储过程，它选择了最大的Id编号，代码就在这里

 ALTER PROCEDURE MaxCustomerId 

 AS
 BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

  SELECT CustomerId 
  FROM tblCustomer 
 WHERE CustomerId=(SELECT max(CustomerId) FROM tblCustomer)

 END

Visual Basic循环查询结果

2 个答案: