OleDbException：沒有給出一個或多個必需參數的值

Question

當前問題：當在本地運行asmx文件以檢查它是否正常工作時，不斷出現的錯誤是沒有給出值，如下所示。現在我已經添加了參數，但錯誤仍然出現。

但是現在，我覺得錯誤不在asmx中，因爲人們已經改變了SQL以正確運行。這是傳遞所需信息的aspx文件。傳遞已設置的會話變量是否存在問題？

Dim Secure As New Visa.VISAServices() 
    Dim authHeader As New Visa.AuthenticationHeader() 

    authHeader.username = "HSBC" 
    authHeader.password = "password" 
    Secure.AuthenticationHeaderValue = authHeader 

    Session("sessionsortnum") = sortnum.Text 
    Session("sessionaccount") = account.Text 


    'Change type for the sortcode 
    Dim sortcode As String = CType(Session.Item("sessionsortnum"), String) 
    Dim accountnumber As String = CType(Session.Item("sessionaccount"), String) 

    lblVisa.Text = Secure.AuthenticateCardSecure(pin.Text, sortnum.Text, account.Text) 

    'NEEDS TO STAY HERE DO NOT MOVE! 
    Session("sessioncase") = lblVisa.Text 
    Dim selectcase As String = CType(Session.Item("sessioncase"), String) 

    'Tests - Being sent to the session var 
    testsort.Text = sortcode 
    testbank.Text = accountnumber 
    testselectc.Text = selectcase 

這是怎樣的會議正在從被連接到與SORTCODE，ACCOUNTNUMBER和selectcase都正確顯示一個服務傳遞。

這是調用ASMX文件：

Private Sub checkbalance(ByVal sender As Object, ByVal e As System.EventArgs) 

    Dim sortcode As String = CType(Session.Item("sessionsortnum"), String) 
    Dim accountnumber As String = CType(Session.Item("sessionaccount"), String) 
    Dim selectcase As String = CType(Session.Item("sessioncase"), String) 
    testsort.Text = sortcode 
    testbank.Text = accountnumber 
    testselectc.Text = selectcase 

    Select Case testselectc.Text 
     Case "1111111111" 
      'Dim lloydsbalance As New Lloyds. 
      'screen.Text = lloydsbalance.overdraft(accountnumber) 
     Case "2222222222" 
      Dim barclaysbalance As New Barclays.Transactions() 
      screen.Text = barclaysbalance.overdraft(accountnumber, sortcode) 
     Case "3333333333" 
      Dim santanderbalance As New Santander.Santander() 
      screen.Text = santanderbalance.overdraft(accountnumber, sortcode) 
Case "4444444444" 
Dim HSBCbalance As New HSBC.HSBC() 
screen.Text = HSBCbalance.OverDraft(accountnumber) 

     Case "5555555555" 
      Dim halifaxbalance As New Halifax.Halifax() 
      screen.Text = halifaxbalance.overdraft(accountnumber) 
     Case "6666666666" 
      Dim natwestbalance As New Natwest.natwest() 
      screen.Text = natwestbalance.overdraft(accountnumber, sortcode) 

    End Select 
End Sub 

原來的問題：每當我在本地運行ASMX只是爲了檢查如果是工作，我只是得到一個錯誤。我檢查了我正在調用的函數，但是我找不到該錯誤。我希望有人能夠發現我做錯了什麼。

錯誤：

System.Data.OleDb.OleDbException: No value given for one or more required parameters. at System.Data.OleDb.OleDbCommand.ExecuteCommandTextErrorHandling(OleDbHResult hr) at System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult(tagDBPARAMS dbParams, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommandText(Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommand(CommandBehavior behavior, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) at System.Data.OleDb.OleDbCommand.ExecuteReader(CommandBehavior behavior) at HSBC.over(Int64 accountnumber) at HSBC.OverDraft(Int64 accountnumber)

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
'             Overdraft Call 
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

<WebMethod()> Public Function OverDraft(ByVal accountnumber As Long) As String 
    Return over(accountnumber) 
End Function 

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
'         Overdraft function 
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

'Creates a service web method 

Private Function over(ByVal accountnumber As Long) As String 
    'Open the connection to the database 

    Dim BalanceDr As OleDbDataReader 
    Dim connectioncmd As OleDbCommand 
    Dim connection As OleDbConnection 
    Dim connx As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.MapPath("../database/HSBc.mdb") & ";" 
    Dim SQL As String = "SELECT Customer_Overdraft FROM Customer WHERE Account_Number=?" 
    Dim overdraft As String 
    connection = New OleDbConnection(connx) 
    connectioncmd = New OleDbCommand(SQL, connection) 
    connection.Open() 
    'Create a DataReader that will return information. 
    BalanceDr = _ 
    connectioncmd.ExecuteReader(CommandBehavior.CloseConnection) 

    If BalanceDr.Read() Then 
     'A row was returned 
     overdraft = BalanceDr(0) 
    Else 
     'A row was not returned 
     overdraft = "No Balance For Account Found" 
    End If 
    BalanceDr.Close() 
    Return overdraft 
End Function 

ACCOUNTNUMBER被存儲在被帶回由其他人創建的服務的會話，我知道這是得到正確傳遞如初頁面上我檢查，這是正確的一個被髮送和使用。

任何人有任何建議嗎？我還將所有必需的權限添加到數據庫中。

Answer 1

非常接近;您的查詢：

"SELECT Customer_Overdraft FROM Customer WHERE Account_Number=?" 

是參數化查詢;因此需要將OleDbParameter添加到命令對象。然後

你的功能應該類似於（不近的Visual Studio所以不能語法檢查）：

Private Function over(ByVal accountnumber As Long) As String 

    'Open the connection to the database 

    Dim BalanceDr As OleDbDataReader 
    Dim connectioncmd As OleDbCommand 
    Dim connection As OleDbConnection 
    Dim connx As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.MapPath("../database/HSBc.mdb") & ";" 
    Dim SQL As String = "SELECT Customer_Overdraft FROM Customer WHERE Account_Number=?" 
    Dim overdraft As String 
    connection = New OleDbConnection(connx) 
    connectioncmd = New OleDbCommand(SQL, connection) 
    'Add A Parameter! 
    connectioncmd.Parameters.AddWithValue("accnumber", accountnumber) 

    connection.Open() 

    'Create a DataReader that will return information. 
    BalanceDr = _ 
    connectioncmd.ExecuteReader(CommandBehavior.CloseConnection) 

    If BalanceDr.Read() Then 
     'A row was returned 
     overdraft = BalanceDr(0) 
    Else 
     'A row was not returned 
     overdraft = "No Balance For Account Found" 
    End If 
    BalanceDr.Close() 
    Return overdraft 
End Function 

我也建議你使用using聲明。這一點尤其重要，因爲您並未明確地關閉數據庫連接，而是依賴於將調用BalanceDr.Close（）的事實。 '使用'將爲您簡化這一點。然後

你的功能將類似於太：

Private Function over(ByVal accountnumber As Long) As String 

    'Open the connection to the database 

    Dim BalanceDr As OleDbDataReader 
    Dim connectioncmd As OleDbCommand 
    Dim connection As OleDbConnection 
    Dim connx As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.MapPath("../database/HSBc.mdb") & ";" 
    Dim SQL As String = "SELECT Customer_Overdraft FROM Customer WHERE Account_Number=?" 
    Dim overdraft As String 

    Using connection = New OleDbConnection(connx) 
     Using connectioncmd = New OleDbCommand(SQL, connection) 
      'Add A Parameter! 
      connectioncmd.Parameters.AddWithValue("accnumber", accountnumber) 

      connection.Open() 

      'Create a DataReader that will return information. 
      Using BalanceDr = connectioncmd.ExecuteReader() 

      If BalanceDr.Read() Then 
       'A row was returned 
       overdraft = BalanceDr(0) 
      Else 
       'A row was not returned 
       overdraft = "No Balance For Account Found" 
      End If 

     End Using 

     End Using 
    End Using 

    Return overdraft 

End Function 

Answer 2

您需要在命令的參數設置爲你的ACCOUNTNUMBER傳遞進來：

connectioncmd = New OleDbCommand(Sql, connection) 
     Dim p As OleDb.OleDbParameter = connectioncmd.CreateParameter() 
     p.Value = accoutnumber 
     connectioncmd.Parameters.Add(p)