在 case 语句中使用枚举仅使用 Case 1 (Visual Basic)

Posted 2023-05-07

【中文标题】在 case 语句中使用枚举仅使用 Case 1 (Visual Basic)

【英文标题】：Only uses Case 1 using enumeration in case statement (Visual Basic)

【发布时间】：2013-10-15 01:48:22

【问题描述】：

该程序应该使用在 Select Case 语句中开头声明的枚举类型。当我运行程序时，无论我选择哪个运算符，它都只使用第一个 case 语句（用于添加）。我尝试在 case 语句中重新排列它们以查看它是否只使用了第一个，但它仍然只是选择了添加。我做错了什么？

Public Class Assignment2Calculator

    Dim Operand1 As Decimal
    Dim Operand2 As Decimal
    Dim CalcOperator As Integer

    Enum OperatorEnum
        add
        divide
        multiply
        subtract
    End Enum

    Private Sub Assignment2Calculator_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        cboOperator.DataSource = [Enum].GetValues(GetType(OperatorEnum))
        AcceptButton = btnCalculate

    End Sub

    Private Sub IsValidData(ByVal txtOperand1 As Object, ByVal txtOperand2 As Object)
        Operand1 = Convert.ToDecimal(txtOperand1.Text)
        Operand2 = Convert.ToDecimal(txtOperand2.Text)

        If (Operand1 > 0 Or Operand1 < 1000000) And (Operand2 > 0 Or Operand2 < 1000000) Then
            If IsNumeric(Operand1) And IsNumeric(Operand2) Then

            End If
        Else
            MessageBox.Show("Operand 1 or 2 is not valid")
        End If

    End Sub

    Private Sub btnCalculate_Click(sender As System.Object, e As System.EventArgs) Handles btnCalculate.Click

        IsValidData(txtOperand1, txtOperand2)


        Calculate(Operand1, Operand2, CalcOperator)


    End Sub


    Private Sub Calculate(ByVal Operand1 As Decimal, ByVal Operand2 As Decimal, _
                          ByVal CalcOperator As Integer)
        'Performs requested operation using select case and enumeration

        Dim answer As Decimal
        Dim CalcOperatorCase As OperatorEnum

        Select Case CalcOperatorCase
            Case Is = OperatorEnum.add

                answer = Operand1 + Operand2
                txtResult.Text = FormatNumber(answer, 3)

            Case Is = OperatorEnum.divide
                answer = Operand1 - Operand2
                txtResult.Text = FormatNumber(answer, 3)

            Case Is = OperatorEnum.multiply
                answer = Operand1 * Operand2
                txtResult.Text = FormatNumber(answer, 3)

            Case Is = OperatorEnum.subtract
                answer = Operand1 / Operand2
                txtResult.Text = FormatNumber(answer, 3)

            Case Else
                MessageBox.Show("Please select an operator")

        End Select

    End Sub


End Class 

【问题讨论】：

您对无效操作数的测试似乎是错误的。如果 Operand1 是 -1，它仍然会通过 If 测试。您应该将 Or 更改为 AndAlso。

【参考方案1】：

您从不分配CalcOperator，因此它始终是整数的默认值，即0 - 在您的enum 中为add。

您可以添加一个事件以在您的ComboBox 更改时更改它，或者您可以在btnCalculate_Click 上进行更改。如果您在其他任何地方都不需要它，不妨在Click 事件中进行：

CalcOperator = CType(cboOperator.SelectedItem, OperatorEnum)

【讨论】：

非常感谢！我非常感谢您的帮助