大酒杯项目无法更新Access数据库

我有一个简单的二十一点游戏，我试图通过添加2个简单的值来更新数据库。我希望它将用户名和玩家的分数添加到数据库中。大酒杯项目无法更新Access数据库

看的在线教程后，这是我试过的代码：

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

我得到的错误：

one or more variables is not provided

我第一次打的保存按钮。第二次它打破了应用程序，它说我“不能调整文件目前的状态已经打开，然后它突出myConnection.ConnectionString = connString

来源

2017-07-27 Derek

你忘了'around'NEW'，所以它认为它是一个列名，对于访问表中没有找到的所有名称都是参数。 – litelite

此外，您的代码有[SQL注入]（https://stackoverflow.com/questions/601300/what-is-sql-injection）的风险，您应该使用具有适当参数的预准备语句。 – litelite

你的第二个问题。这是因为您必须在尝试重新打开数据库之前关闭数据库。目前只有在查询没有抛出任何东西时才关闭数据库。您应该将连接关闭到['Finally'块]（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'块]（https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/using-statement） – litelite

考虑实施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.

下面是一些示例代码：

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

    con.Open() 

    cmd.ExecuteNonQuery() 

End Using

这将处理关闭和你的对象的处置。

我也会考虑使用参数来避免SQL注入。有关详细信息，请参阅Bobby Tables。

下面是一些示例代码：

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.

随着OleDb你参数的顺序是非常重要的，而不是命名。确保您创建参数，如上所示，它们出现在您的命令中。

来源

2017-07-27 15:17:40 Bugs

大酒杯项目无法更新Access数据库

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