试块VB.NET中的算术问题

我对VB.NET和一般编程都比较陌生，所以我还在学习语法的基础知识

我一直收到一个错误，上面写着

预期报表结束

在线

（b\0+1=1）

。我将如何结束此操作以解决错误？谢谢您的回复

b = InputBox("Please Enter Radius.") 'enter radius
  Try (b\0+1 = 1)
     Exit Try
   Catch ex As NullReferenceException
     Console.WriteLine("Not a whole number. Please try again")
     Console.ReadLine()
      Exit Try
   End Try

---

很可能用户输入的不是整数，所以请做好准备。你几乎做到了，但不是很好。你想算出一个非整数。但是非数字输入，比如“abc”呢？在所有情况下，最好假设用户可能输入了错误的输入，并使用逻辑进行检查。您应该使用

If..Else

而不是

Try..Catch

来处理该逻辑

我还选择使用

Mod

，因为我不知道

（b\0+1=1）

应该做什么。

\

对数字进行四舍五入，丢弃任何余数，这样对您没有帮助。使用

Decimal

数据类型覆盖无限小的余数，即

1.00000000000000000000001

（但不能少于。请参阅）。请注意，

D

强制执行

Mod

运算符的操作数

' I added declaration of 'b' here, assuming it's a string since InputBox returns string.
Dim b As String
b = InputBox("Please Enter Radius.")
Console.WriteLine("You entered {0}", b)
Dim radius As Decimal
If Decimal.TryParse(b, radius) Then ' True if it's a number
    If radius Mod 1D = 0D Then ' True if it has no remainder
        Console.WriteLine("You entered an integral number. Good job")
    Else
        Console.WriteLine("Not a whole number. Please try again")
    End If
Else
    Console.WriteLine("Not even a number. Please try again")
End If
Console.ReadLine()

“预期语句结束”意味着您在一行代码上付出的比预期的要多。在这种情况下，这是因为

Try

必须在自己的行上

对于确定用户是否输入了整数的问题，将文本转换为整数的有用方法是and方法。前者在出现错误时抛出异常，而后者返回一个布尔值，指示解析是否成功

“NullReferenceException”不是您想要捕获的内容：您应该查阅文档，了解可以引发异常的方法，看看它可以引发哪些异常。有时捕获任何异常就足够了：

Module Module1

    Sub Main()
        Dim b As String
        Dim isGoodNumber As Boolean = True
        Dim radius As Integer

        ' OPTION ONE: Decline any bad input with a generic error message.
        Do
            b = InputBox("Please enter the radius as a whole number:")
            Console.WriteLine("You entered {0}", b)
            Try
                radius = Integer.Parse(b)
                isGoodNumber = True
            Catch ex As Exception
                isGoodNumber = False
            End Try

            If Not isGoodNumber Then
                Console.WriteLine("Please enter a whole number.")
            End If

        Loop Until isGoodNumber

        Console.ReadLine()

    End Sub

End Module

Module Module1

    Sub Main()
        Dim b As String
        Dim isGoodNumber As Boolean = True
        Dim radius As Integer

        ' OPTION THREE: A shorter way of option one.
        Do
            b = InputBox("Please enter the radius as a whole number:")
            Console.WriteLine("You entered {0}", b)
            isGoodNumber = Integer.TryParse(b, radius)
            If Not isGoodNumber Then
                Console.WriteLine("Please enter a whole number.")
            End If

        Loop Until isGoodNumber

        Console.ReadLine()

    End Sub

End Module

如果要根据抛出的错误执行不同的操作，可以使用几个

Catch

子句：

Module Module1

    Sub Main()
        Dim b As String
        Dim isGoodNumber As Boolean = True
        Dim radius As Integer

        ' OPTION TWO: Decline any bad input with a more specific error message.
        Do
            b = InputBox("Please enter the radius as a whole number:")
            Console.WriteLine("You entered {0}", b)
            Try
                radius = Integer.Parse(b)
                isGoodNumber = True
            Catch ex As ArgumentNullException
                isGoodNumber = False
                Console.WriteLine("Please enter a whole number.")
            Catch ex As FormatException
                isGoodNumber = False
                Console.WriteLine("Please enter a whole number.")
            Catch ex As OverflowException
                isGoodNumber = False
                Console.WriteLine("Please enter a whole number between {0} and {1}", Integer.MinValue, Integer.MaxValue)
            End Try

        Loop Until isGoodNumber

        Console.ReadLine()

    End Sub

End Module

在这种情况下，如果不需要给出错误的输入相关错误消息，甚至不需要抛出异常：

Module Module1

    Sub Main()
        Dim b As String
        Dim isGoodNumber As Boolean = True
        Dim radius As Integer

        ' OPTION ONE: Decline any bad input with a generic error message.
        Do
            b = InputBox("Please enter the radius as a whole number:")
            Console.WriteLine("You entered {0}", b)
            Try
                radius = Integer.Parse(b)
                isGoodNumber = True
            Catch ex As Exception
                isGoodNumber = False
            End Try

            If Not isGoodNumber Then
                Console.WriteLine("Please enter a whole number.")
            End If

        Loop Until isGoodNumber

        Console.ReadLine()

    End Sub

End Module

Module Module1

    Sub Main()
        Dim b As String
        Dim isGoodNumber As Boolean = True
        Dim radius As Integer

        ' OPTION THREE: A shorter way of option one.
        Do
            b = InputBox("Please enter the radius as a whole number:")
            Console.WriteLine("You entered {0}", b)
            isGoodNumber = Integer.TryParse(b, radius)
            If Not isGoodNumber Then
                Console.WriteLine("Please enter a whole number.")
            End If

        Loop Until isGoodNumber

        Console.ReadLine()

    End Sub

End Module

---

Try/Catch定义了一个块——所有的代码都应该放在它里面。你不能指定一个语句来尝试那样做，如果这就是你要做的，如果你把b除以0，你就不能这样做。你到底想做什么？你还需要打开Option Strict。InputBox返回一个字符串，您（显然）正在尝试对其进行数学运算。我不知道你想用

（b\0+1=1）

做什么，但这是错误的。您需要指定结果，但您所应用的任何测试都是错误的。你真的不需要尝试/捕捉在“VB.net Try sample”上进行快速的谷歌搜索，就会发现…samples

如果q=Int（q），则

应告诉您它是否为整数

q

将是用户输入字符串的解析值