Question

如何将查询结果转换为变量并将其显示在标签中。我曾尝试使用DR.Read和While DR.Read，但仍然失败。这是我的代码示例

Public dataCNN As New MySqlConnection
Public dataCMD As New MySqlCommand
Public DR As MySqlDataReader
Public DA As MySqlDataAdapter
Public DT As DataTable
Public QUERY As String

Public Sub dbConnection()
    dataCNN = New MySqlConnection
    dataCNN.ConnectionString = "server=localhost;userid=root;password=password;database=data"
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Call dbConnection()
    txt1.Focus()
    dataCNN.Open()
    QUERY = "SELECT * FROM data.numbering WHERE id=1"
    dataCMD = New MySqlCommand(QUERY, dataCNN)
    DR = dataCMD.ExecuteReader()

    If DR.HasRows Then
        While DR.Read
            Label1.Text = DR("number").ToString()
        End While
    End If
    dataCNN.Close()
End Sub 

Private Sub txt1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txt1.KeyPress
    Dim a, b, c As Integer
    If (Val(Asc(e.KeyChar) = 33)) Then
        Label2.Text = "Teller 1 is now serving number"
        a = Label1.Text + 1

        Label1.Text = a
        DA = New MySqlDataAdapter("UPDATE data.numbering SET number='" & a & "' WHERE id=1", dataCNN)
    End If
    'MsgBox("" & Val(Asc(e.KeyChar)))
End Sub

Answer 1

你应该添加，

DR = dataCMD.ExecuteReader()

后

dataCMD = New MySqlCommand(QUERY, dataCNN)

编辑：如您对更新的评论中所述，您可以这样做

Using connection As New MySqlConnection(connectionString)
    Dim  Mycmd As New MySqlCommand(yourquery, connection)
     Mycmd.Connection.Open()
     Mycmd.ExecuteNonQuery()
End Using

如果您使用'使用'，则无需关闭连接。

如何将查询结果转换为变量并将其显示在标签中

1 个答案: