如何通過vb.net在mysql數據庫中的標簽中顯示所選值

Question

我有一個代碼，但是沒有用。 我試圖在label2中添加一個值，但是它不起作用。 請幫我。

Private Sub student_no_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles student_no.Click
    MySqlConnection = New MySqlConnection
    MySqlConnection.ConnectionString = "server = localhost; port=3307; user id = root; password = 1234; database = sample;"
    Dim READER As MySqlDataReader

    Try
        MySqlConnection.Open()
        Dim query As String
        query = " select id from sample.student where last_name = '" & txtlastname.Text & "' "
        Dim Command As New MySqlCommand(query, MySqlConnection)
        READER = Command.ExecuteReader
        Label2.Text = query.ToString

        MessageBox.Show("Student Number Generated")
        MySqlConnection.Close()

    Catch ex As Exception
        MessageBox.Show(ex.Message)
    Finally
        MySqlConnection.Dispose()

    End Try

End Sub

Answer 1

您在查詢中使用.ToString，這是一個字符串。 您應該做的是對READER對象的操作。

由於SELECT總是會返回結果列表，因此您必須將結果視為此類，例如...

While READER.Read()
  MessageBox.Show((READER.GetInt32(0)))
End While

.Read（）返回返回的行集中的下一個元素

Answer 2

If READER.Read() Then
    Label2.Text = READER.GetString(0)
End If