2

这是在 Mono 中运行良好的 .cs 文件：

using System;

public class HelloWorld
{
    static public void Main ()
    {
    Console.WriteLine("Enter a number");

    int UserNumber = int.Parse(Console.ReadLine());

    Console.WriteLine("Your number is: " + UserNumber);
    }
}

我在 Xamarin 中打开了这个 Test.cs 文件，它工作正常。然后我选择 'Run' > 'Start without Debugging' 并在显示面板中弹出这些错误：

Enter a number

Unhandled Exception:
System.ArgumentNullException: Argument cannot be null.
Parameter name: String
  at System.Number.StringToNumber (System.String str, NumberStyles options, System.NumberBuffer& number, System.Globalization.NumberFormatInfo info, Boolean parseDecimal) [0x00054] in /private/tmp/source-mono-mac-4.0.0-branch-c5sr2/bockbuild-mono-4.0.0-branch/profiles/mono-mac-xamarin/build-root/mono-4.0.2/external/referencesource/mscorlib/system/number.cs:1084 
  at System.Number.ParseInt32 (System.String s, NumberStyles style, System.Globalization.NumberFormatInfo info) [0x00014] in /private/tmp/source-mono-mac-4.0.0-branch-c5sr2/bockbuild-mono-4.0.0-branch/profiles/mono-mac-xamarin/build-root/mono-4.0.2/external/referencesource/mscorlib/system/number.cs:755 
  at System.Int32.Parse (System.String s) [0x00000] in /private/tmp/source-mono-mac-4.0.0-branch-c5sr2/bockbuild-mono-4.0.0-branch/profiles/mono-mac-xamarin/build-root/mono-4.0.2/external/referencesource/mscorlib/system/int32.cs:140 
  at HelloWorld.Main () [0x0000b] in /Users/Yardenbourg/Desktop/Test.cs:9 
[ERROR] FATAL UNHANDLED EXCEPTION: System.ArgumentNullException: Argument cannot be null.
Parameter name: String
  at System.Number.StringToNumber (System.String str, NumberStyles options, System.NumberBuffer& number, System.Globalization.NumberFormatInfo info, Boolean parseDecimal) [0x00054] in /private/tmp/source-mono-mac-4.0.0-branch-c5sr2/bockbuild-mono-4.0.0-branch/profiles/mono-mac-xamarin/build-root/mono-4.0.2/external/referencesource/mscorlib/system/number.cs:1084 
  at System.Number.ParseInt32 (System.String s, NumberStyles style, System.Globalization.NumberFormatInfo info) [0x00014] in /private/tmp/source-mono-mac-4.0.0-branch-c5sr2/bockbuild-mono-4.0.0-branch/profiles/mono-mac-xamarin/build-root/mono-4.0.2/external/referencesource/mscorlib/system/number.cs:755 
  at System.Int32.Parse (System.String s) [0x00000] in /private/tmp/source-mono-mac-4.0.0-branch-c5sr2/bockbuild-mono-4.0.0-branch/profiles/mono-mac-xamarin/build-root/mono-4.0.2/external/referencesource/mscorlib/system/int32.cs:140 
  at HelloWorld.Main () [0x0000b] in /Users/Yardenbourg/Desktop/Test.cs:9 
The application was terminated by a signal: SIGHUP

我不确定这里的问题是什么。会不会和这条线有关？

int UserNumber = int.Parse(Console.ReadLine());
4

2 回答 2

3

阅读堆栈跟踪，它说 Parse 的方法传递了一个 null 参数，但它不能为 null。尝试拆分读取行和解析，然后确保该行不为空或为空。

public class HelloWorld
{
    static public void Main ()
    {
    Console.WriteLine("Enter a number");
    String input = Console.ReadLine();
    int UserNumber = 0;
    if(input != null && input != "")
    {
        UserNumber = int.Parse(input);
    }

    Console.WriteLine("Your number is: " + UserNumber);
    }
}

像这样拆分代码更容易阅读和调试。

于 2015-07-28T15:26:03.613 回答
1

我打赌你正在使用一个C# -> Mac -> Xamarin.Mac项目。默认情况下，这些程序不使用交互式控制台，您在调用Console.ReadLine().

尝试创建一个新的解决方案；而是选择C# -> Console Project让交互式控制台工作。

于 2015-07-28T16:14:46.770 回答