Question

我有這個函數從數據庫返回學生的具體信息。 這是代碼。

Public Function arrInfo(Byval id as String) 
    Dim name as String = "" 
    DBCon_Open() 
    Dim Cmd = New MySqlCommand("SELECT * FROM student WHERE student_id ='" & id & "'", con) 
    Cmd.CommandTimeout = 0 
    Dim rs = Cmd.ExecuteReader 

    Do While rs.Read 
     name = rs.Item("firstname") 
    Loop 
    rs.Close() 
    Cmd.Dispose() 
    DBCon_Close() 

    Return name 

End Function 

MSGBOX（arrInfo（ 「STUD0027」））

結果：本

但是，我想返回從查詢學生的信息的數組。

當我把它叫做是這樣的功能：

MSGBOX（arrInfo（ 「STUD0027」）（ 「姓氏」））

我想這一個，但不工作。

Public Function arrInfo(Byval id as String) 

    DBCon_Open() 
    Dim Cmd = New MySqlCommand("SELECT * FROM student WHERE student_id ='" & id & "'", con) 
    Cmd.CommandTimeout = 0 
    Dim rs = Cmd.ExecuteReader 
    rs.Close() 
    Cmd.Dispose() 
    DBCon_Close() 

    Return rs.Read 

End Function 

我該如何實現這個數組返回？

非常感謝任何幫助。

感謝

Answer 1

試試這個：

Public Iterator Function arrInfo(Byval id as String) As IEnumerable(Of IDataRecord) 
    'In most cases, the best practice in .Net is to use a new connection object each time, to take advantage of connection pooling 
    Using cn As New MySqlConnection(DBCon.ConnectionString), _ 
      cmd As New MySqlCommand("SELECT * FROM student WHERE student_id = @id", cn) 

     cmd.Parameters.Add("@id", MySqlDbType.VarChar, 8).Value = id 
     cn.Open() 

     Using rdr = cmd.ExecuteReader() 
      While rdr.Read() 
       Yield Return rdr 
      End While 
      rdr.Close() 
     End Using 
    End Using 'Using block will close and dispose your connection, **even if an exception is thrown**. The existing code would have left it hanging open. 
End Function 

這不正是數組，但它有一些相似的性質。您可以使用它像這樣：

For Each record As IDataRecord In arrInfo("STUD0027") 
    MsgBox(String.Format("Name: {0} {1}", record("firstname"), record("lastname"))) 
Next record 

你也應該看看DataTable和DataSet對象。