Button 在vb.net中用visual basic创建windows窗体

最后第三行代码显示“未声明或无法访问”。为什么？ 公开课表格1 私有子表单1_Load（发送方作为对象，e作为事件参数）处理MyBase.Load

End Sub

Private Sub Label3_Click(sender As Object, e As EventArgs) Handles Label3.Click

End Sub

Private Sub Label4_Click(sender As Object, e As EventArgs) Handles Label4.Click

End Sub

Private Sub TextBox7_TextChanged(sender As Object, e As EventArgs)

End Sub

Private Sub Label22_Click(sender As Object, e As EventArgs) Handles Label22.Click

End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim num1, num2, num3, num4, Total, obtains, Grade, percentsge As Integer

    num1 = txtN.Text
    num2 = txtA.Text
    num3 = txtVb.Text
    num4 = txtGM.Text
    'total marks
    obtains = num1 + num2 + num3 + num4
    lblobtains.Text = obtains  :-it shows ,it is not declared or can't access????


End Sub

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