大酒杯項目無法更新Access數據庫

我有一個簡單的二十一點遊戲，我試圖通過添加2個簡單的值來更新數據庫。我希望它將用戶名和玩家的分數添加到數據庫中。大酒杯項目無法更新Access數據庫

看的在線教程後，這是我試過的代碼：

Imports System.Data.OleDb 

Public Class Form1 

    'for updating database 
    Dim provider As String 
    Dim dataFile As String 
    Dim connString As String 
    Dim myConnection As OleDbConnection = New OleDbConnection 

    Private Sub ButtonSaveScore_Click(sender As Object, e As EventArgs) Handles ButtonSaveScore.Click 

     provider = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" 
     dataFile = "F:\Documents\Class Documents\CSC289 - K6A - Programming Capstone Project\Project\BlackJack\BlackJack\Scoreboard.accdb" 
     connString = provider & dataFile 
     myConnection.ConnectionString = connString 
     myConnection.Open() 
     Dim str As String 
     str = "Update [Scores] set [UserName] = '" & playerName & "',[Score] =' " & wins & "' where [ID] = NEW" 
     Dim cmd As OleDbCommand = New OleDbCommand(str, myConnection) 

     Try 
      cmd.ExecuteNonQuery() 
      cmd.Dispose() 
      myConnection.Close() 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 

    End Sub

我得到的錯誤：

one or more variables is not provided

我第一次打的保存按鈕。第二次它打破了應用程序，它說我「不能調整文件目前的狀態已經打開，然後它突出myConnection.ConnectionString = connString

來源

2017-07-27 Derek

你忘了'around'NEW'，所以它認爲它是一個列名，對於訪問表中沒有找到的所有名稱都是參數。 – litelite

此外，您的代碼有[SQL注入]（https://stackoverflow.com/questions/601300/what-is-sql-injection）的風險，您應該使用具有適當參數的預準備語句。 – litelite

你的第二個問題。這是因爲您必須在嘗試重新打開數據庫之前關閉數據庫。目前只有在查詢沒有拋出任何東西時才關閉數據庫。您應該將連接關閉到['Finally'塊]（https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/try-catch-finally-statement）。或者，您可以使用['使用'塊]（https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/using-statement） – litelite

考慮實施Using：。

Sometimes your code requires an unmanaged resource, such as a file handle, a COM wrapper, or a SQL connection. A Using block guarantees the disposal of one or more such resources when your code is finished with them. This makes them available for other code to use.

下面是一些示例代碼：

Using con As New OleDbConnection(connectionString), 
     cmd As New OleDbCommand(commandString, con) 

    con.Open() 

    cmd.ExecuteNonQuery() 

End Using

這將處理關閉和你的對象的處置。

我也會考慮使用參數來避免SQL注入。有關詳細信息，請參閱Bobby Tables。

下面是一些示例代碼：

Using con As New OleDbConnection(connectionString), 
     cmd As New OleDbCommand("UPDATE [Scores] SET [UserName] = ?, [Score] = ? WHERE [ID] = ?", con) 

    con.Open() 

    cmd.Parameters.Add("@Username", OleDbType.[Type]).Value = playerName 
    cmd.Parameters.Add("@Score", OleDbType.[Type]).Value = wins 

    'I've popped this into a parameter as I'm unsure what it is. I'll leave that for you to decide 
    cmd.Parameters.Add("@ID", OleDbType.[Type]).Value = "NEW" 

    cmd.ExecuteNonQuery() 

End Using

Note that I have used OleDbType.[Type] . You will want to replace this with the data type you have specified for your columns.

隨着OleDb你參數的順序是非常重要的，而不是命名。確保您創建參數，如上所示，它們出現在您的命令中。

來源

2017-07-27 15:17:40 Bugs

大酒杯項目無法更新Access數據庫

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