Question

我正在玩学习VB.NET，通过制作一个基本的计算器并使代码慢慢变得更复杂，开始玩类和问题并遇到这个错误（见标题）并且无法理解什么它的意思是。这是我的完整代码：

Class Calculator

    Private _num1, _num2, _result As Double
    Private _operation, _output() As String
    Private _ressuc As Boolean = True

    Public Function input() As String()
        Console.Write("Enter your first number: ")
        _num1 = Console.ReadLine()
        Console.Write("Operation? (Add, Subtract, Divide, Multiply, Modulus, Power): ")
        _operation = Console.ReadLine()
        Console.Write("Enter your second number: ")
        _num2 = Console.ReadLine()

        _output = calculate(_num1, _num2, _operation)

        Return _output

    End Function

    Private Function calculate(num1 As Integer, num2 As Integer, operation As String) As String
        Dim result As Double = Nothing
        Dim ressuc As Boolean = True

        Select Case operation
            Case "add", "+"
                result = num1 + num2
            Case "subtract", "-"
                result = num1 - num2
            Case "divide", "/"
                result = num1 / num2
            Case "multiply", "*"
                result = num1 * num2
            Case "modulus", "%", "mod"
                result = num1 Mod num2
            Case "power", "^"
                result = num1 ^ num2
            Case Else
                ressuc = False
        End Select

        If ressuc Then
            calculate = ("Your answer is: " & result.ToString())
        Else
            calculate = ("Function '" & operation & "' not available.")
        End If

    End Function

End Class


Module Module1

    Sub Main()
        Dim calc As Calculator = New Calculator()
        Console.WriteLine(calc.input())
        Console.ReadLine()
    End Sub

End Module

错误存在于此处：

_output = calculate(_num1, _num2, _operation)

计算函数（及其变量）带有下划线，并在标题中显示错误。有人可以向我解释为什么字符串不会从＆＃39;计算＆＃39;以及如何解决它？

Answer 1

尝试从声明中的()和output()函数的String()返回类型中删除input

Class Calculator

    Private _num1, _num2, _result As Double
    Private _operation, _output As String
    Private _ressuc As Boolean = True

    Public Function input() As String
        Console.Write("Enter your first number: ")

这样做的原因是，当您声明以()结尾的变量或使用As关键字然后使用以()结尾的类型时，您告诉它您想要一个那种类型的数组。因此，您可以从代码中删除()，也可以将它们留在那里并访问所有项目，就像它们是数组一样。由于您没有访问或使用它们作为数组，因此更容易删除有问题的()。

Answer 2

您已将变量_output定义为String Array ：

Private _output() As String与Private _output As String()

相同

尝试从声明中删除括号，因为它看起来不应该使用字符串数组。

Private _output As String

类型的值＆＃39;字符串＆＃39;无法转换为＆＃39; 1维数组的字符串＆＃39;

2 个答案: