MysqlDataReader.Read停留在最後一個記錄和犯規EOF

Question

我困惑，爲什麼mySqlDataReader.Read停留在最後一個記錄和犯規EOF ..

這是我的私人的ExecuteSQL功能：

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 

這是發生錯誤我的子叫它：

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 

我是新來vbnet，真的有一個關於它的小知識,,請幫我,,並預先感謝您..

Answer 1

問題是您使用HasRows屬性作爲循環終止表達式。該屬性的值永遠不會改變。讀者有行或者沒有。這不是檢查是否有行要閱讀，所以閱讀沒有效果。

您應該使用Read方法作爲您的標誌。數據讀取器開始時沒有加載行。每次調用Read時，它將加載下一行並返回True，或者如果沒有更多行要讀取，則返回False。

如果您想在結果集爲空時執行特殊操作，通常只使用HasRows，例如，

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

如果你不想把一個空的結果集作爲一個特殊的情況，那麼只需撥打Read：

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

注意，試圖調用Read會拋出異常之前訪問任何數據。