MysqlDataReader.Read 停留在最后一条记录上，没有 EOF

Question

我很困惑为什么 mySqlDataReader.Read 停留在最后一条记录上而不是 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

这是我在发生错误的地方调用它的子程序：

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，对它了解不多，请帮助我，在此先感谢您..

Answer 1

问题是您使用 HasRows 属性作为循环终止表达式。属性的值永远不会改变。 reader 要么有行，要么没有。这不是检查它是否还有行要读取，因此读取无效。

你应该使用 Read 方法作为你的标志。数据 reader 开始时未加载任何行。每次调用 Read 时，它都会加载下一行和 return True 或者，如果没有更多的行要读取，它会 returns False .

如果你想在结果集为空时做一些特殊的事情，你通常只使用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例，则只需调用 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将引发异常。

MysqlDataReader.Read 停留在最后一条记录上，没有 EOF

MysqlDataReader.Read stuck on the last record and doesnt EOF

vb.net

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