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我很困惑为什么 mySqlDataReader.Read 停留在最后一条记录上并且没有 EOF ..

这是我的 executeSql 私有函数：

Private Function executeSQL(ByVal str As String, ByVal connString As String, ByVal returnRecordSet As Boolean) As Object
    Dim cmd As Object
    Dim objConn As Object
    Try
        If dbType = 2 Then
            cmd = New MySqlCommand
            objConn = New MySqlConnection(connString)
        Else
            cmd = New OleDbCommand
            objConn = New OleDbConnection(connString)
        End If
        'If objConn.State = ConnectionState.Open Then objConn.Close()
        objConn.Open()
        cmd.Connection = objConn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = str
        If returnRecordSet Then
            executeSQL = cmd.ExecuteReader()
            executeSQL.Read()
        Else
            cmd.ExecuteNonQuery()
            executeSQL = Nothing
        End If
    Catch ex As Exception
        MsgBox(Err.Description & " @ExecuteSQL", MsgBoxStyle.Critical, "ExecuteSQL")
    End Try
End Function

这是我的 sub 在发生错误的地方调用它：

Using admsDB As MySqlConnection = New MySqlConnection("server=" & rs("server") & ";uid=" & rs("user") & ";password=" & rs("pwd") & ";port=" & rs("port") & ";database=adms_db;")
                    admsDB.Open()
                    connDef.Close()
                    rs.Close()
                    'get record on admsdb
                    Dim logDate As DateTime
                    Dim str As String
                    str = "select userid, checktime from adms_db.checkinout in_out where userid not in (select userid " &
                        "from adms_db.checkinout in_out join (select str_to_date(datetime,'%d/%m/%Y %H:%i:%s') tgl, fid from zsoft_bkd_padang.ta_log) ta " &
                        "on ta.fid=userid and tgl=checktime)"
                    Dim rsAdms As MySqlDataReader = executeSQL(str, admsDB.ConnectionString, True)
                    Dim i As Integer
                    'This is where the error is, datareader stuck on the last record and doesnt EOF
                    While rsAdms.HasRows
                        'i = i + 1 
                        logDate = rsAdms(1)
                        'save to ta_log
                        str = "insert into ta_log (fid, Tanggal_Log, jam_Log, Datetime) values ('" & rsAdms(0) & "','" & Format(logDate.Date, "dd/MM/yyyy") & "', '" & logDate.ToString("hh:mm:ss") & "', '" & logDate & "')"
                        executeSQL(str, oConn.ConnectionString, False)
                        rsAdms.Read()
                    End While

                    'del record on admsdb
                    str = "truncate table checkinout"
                    executeSQL(str, admsDB.ConnectionString, False)
                End Using

我是vbnet的新手，对它真的有一点了解，请帮助我，并提前谢谢你..

4

1 回答 1

1

问题是您使用该HasRows属性作为循环终止表达式。该属性的值永远不会改变。阅读器要么有行，要么没有。它不是检查它是否还有要读取的行，因此读取没有效果。

您应该使用该Read方法作为您的标志。数据读取器在没有加载行的情况下开始。每次调用Read时，它将加载下一行并返回True，或者，如果没有更多行要读取，则返回False。

您通常仅HasRows在结果集为空时想要做一些特殊的事情时使用，例如

If myDataReader.HasRows Then
    '...
Else
    MessageBox.Show("No matches found")
End If

如果您不想将空结果集视为特殊情况，则只需调用Read：

While myDataReader.Read()
    Dim firstFieldValue = myDataReader(0)
    '...
End While

请注意，在调用之前尝试访问任何数据Read都会引发异常。

于 2016-12-01T05:54:19.593 回答