VB MsgBox vbYesNo未声明

Question

我有简单的程序部分，该错误会引起错误：VB MsgBox是否未声明。

如果重要，请使用Visual Studio Express 2012和Windows 7。

未声明VbYesNo。 由于其保护级别，它可能无法访问。

非常感谢过去没有发生过麻烦。

哪个程序麻烦：

userchoice = MsgBox("Did you mean to enter A?", vbYesNno, "Yes") ' if yes add, if no subtract

所有程序：

Public Class MainForm
Public stroperation, strnumber1, strnumber2, strresult As String
Public decnumber1, decnumber2, decresult As Decimal
Public operation, userchoice
Private Sub calculateButton_Click(sender As Object, e As EventArgs) Handles calculateButton.Click
    operation = operationTextBox.Text
    stroperation = CStr(operation)
    strnumber1 = number1TextBox.Text
    decnumber1 = CDec(strnumber1)
    strnumber2 = number2TextBox.Text
    decnumber2 = CDec(strnumber2)
    If stroperation = "S" Or stroperation = "s" Then
        decresult = decnumber1 - decnumber2
        strresult = CStr(decresult)
        resultLabel.Text = "Difference: " & strresult
    ElseIf stroperation = "A" Or stroperation = "a" Then
        decresult = decnumber1 + decnumber2
        strresult = CStr(decresult)
        resultLabel.Text = "Sum: " & strresult
    Else
        userchoice = MsgBox("Did you mean to enter A?", vbYesNno, "Yes") ' if yes add, if no subtract
        If userchoice = vbYes Then
            decresult = decnumber1 + decnumber2
            strresult = CStr(decresult)
            resultLabel.Text = "Sum: " & strresult
        ElseIf userchoice = vbNo Then
            decresult = decnumber1 - decnumber2
            strresult = CStr(decresult)
            resultLabel.Text = "Difference: " & strresult
        End If
    End If
End Sub

Private Sub MainForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load

End Sub
End Class

Answer 1

您有错字：

userchoice = MsgBox("Did you mean to enter A?", vbYesNno, "Yes") 

注意“ Nn”。 应该是vbYesNo

Answer 2

If MsgBox("Are You Sure ?", vbYesNo, "Yes") = MsgBoxResult.Yes Then            
    MsgBox("Yes")
Else
    MsgBox("No")
End If