Question

我计划在不久的将来创建一个关于测验的项目，现在我正在练习一些代码，这是我的问题。我在private sub Button_Click内有一个变量。所有变量都可以正常工作但我无法在其他Private sub Button3_Click中访问它，因为它是一个私有变量，因此我决定将它们变为公共变量。

然后当我运行它时，它只显示我数据库中的最后一项，然后我返回原始代码并显示数据库中的所有数据，当我检查它时，我从radiobutton创建一个事件自动插入数据进入我的桌子。所以我需要变量标签但我无法在我的活动中访问它。

注意：当数据库具有除panel1，button2和button3之外的数据时，我的所有控件都将以编程方式添加。

这是我的原始代码：

'This is for adding controls like labels and radiobutton dependeng in a number of data from database
 Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
      Try
        Dim conn As OleDbConnection = GetDBConnection()
        Dim cmd As New OleDbCommand("SELECT * FROM tblEcobags ORDER BY N ASC", conn)
        cmd.Prepare()
        Dim dataReader As OleDbDataReader = cmd.ExecuteReader()
        Do While dataReader.Read
            Dim Cpanel As New Panel()
            Dim count As Integer = Panel1.Controls.OfType(Of Panel)().ToList().Count
            count = Panel1.Controls.OfType(Of Panel)().ToList().Count
            Cpanel.Location = New Point(10, (25 * count) * 2.2)
            Cpanel.Size = New Size(537, 51)
            Cpanel.Name = "Cpanel" & (count + 1)
            Cpanel.BackColor = Color.White
            Panel1.Controls.Add(Cpanel)


            Dim label As New Label()
            count = Cpanel.Controls.OfType(Of Label)().ToList().Count
            label.Location = New Point(10, (25 * count))
            label.AutoSize = True
            label.Name = "label_" & (count + 1)
            label.Text = dataReader.Item("N") & "."
            label.Font = New Font(label.Font.FontFamily, 10, FontStyle.Bold)
            Cpanel.Controls.Add(label)

            Dim lblQ As New Label()
            count = Cpanel.Controls.OfType(Of TextBox)().ToList().Count
            lblQ.Location = New System.Drawing.Point(40, 25 * count)
            lblQ.AutoSize = True
            lblQ.Name = "lblQ" & (count + 1)
            lblQ.Text = dataReader.Item("ProductDes")
            lblQ.Font = New Font(lblQ.Font.FontFamily, 11)
            Cpanel.Controls.Add(lblQ)

            Dim rbChoiceA As New RadioButton()
            count = Cpanel.Controls.OfType(Of RadioButton)().ToList().Count
            rbChoiceA.Location = New Point(40, 25)
            rbChoiceA.AutoSize = True
            rbChoiceA.Name = "rb" & (count + 1)
            rbChoiceA.Text = dataReader.Item("Each")
            rbChoiceA.Font = New Font(rbChoiceA.Font.FontFamily, 10)
            AddHandler rbChoiceA.CheckedChanged, AddressOf rbChoiceA_Checked
            Cpanel.Controls.Add(rbChoiceA)

            Dim rbChoiceB As New RadioButton()
            count = Cpanel.Controls.OfType(Of RadioButton)().ToList().Count
            rbChoiceB.Location = New Point(200, 25)
            rbChoiceB.AutoSize = True
            rbChoiceB.Name = "rb" & (count + 1)
            rbChoiceB.Text = dataReader.Item("PerDozen")
            rbChoiceB.Font = New Font(rbChoiceB.Font.FontFamily, 10)
            Cpanel.Controls.Add(rbChoiceB)


        Loop
        Button2.Enabled = False
        conn.Dispose()
        conn.Close()
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End Sub
'this is an event that i can't access my "label" that I add programmatically
Private Sub rbChoiceA_CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)
 Try
        Dim conn As OleDbConnection = GetDBConnection()
        Dim cmd As New OleDbCommand("INSERT INTO tblSubmit(N)VALUES('" & must be label.text & "') ", conn)
        cmd.ExecuteNonQuery()
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End Sub

Answer 1

您可以在数据库或文本文件或SQL或程序中将变量设置为静态比如string myvar = "static";

Answer 2

很抱歉我的描述不好，但我现在已经开始工作了。我曾经在任何函数之外声明它，但我犯的错误是用括号表示变量，我不知道它之间的区别所以我需要知道没有括号的那个。这是我修改过的声明，因此任何函数都必须可以访问

Dim label as Label()

我的button2_Click

事件中的更新代码出错了

label = new label() ' I got error here

但是当我删除声明中的括号时，它就可以了。

Dim label as label

所以我可以问一下它之间的区别是什么，为什么我使用的那个没有工作而不是工作的下面。提前感谢您的回复。

如何从私有子中的变量获取值或者使公共变量不失去价值

2 个答案: