Question

我很困惑为什么mySqlDataReader.Read卡在最后一条记录上而且没有EOF ..

这是我对executeSql的私有函数：

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

这是我的子句，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的新手并且真的对它有一点了解，请帮助我，并提前感谢你..

Answer 1

问题在于您使用HasRows属性作为循环终止表达式。该属性的值永远不会改变。读者有行或者没有行。它不是检查是否还有行要读取，所以读取没有效果。

您应该使用Read方法作为您的旗帜。数据读取器在没有加载行的情况下开始。每次调用Read时，它都会加载下一行并返回True，或者，如果没有其他行要读取，则会返回False。

如果您想在结果集为空时执行某些特殊操作，通常只使用HasRows，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，则只需致电Read：

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

请注意，在调用Read之前尝试访问任何数据都会引发异常。

MysqlDataReader.Read卡在最后一条记录上并且没有EOF

1 个答案: