双到字符串和后退会导致错误

Question

这个简单的程序

using System.IO;
using System;
using System.ComponentModel;

class Program
{
    static void Main()
    {
        var smallDouble = double.MinValue;
        Console.WriteLine(smallDouble);
        var converter = TypeDescriptor.GetConverter(typeof(double));
        var convertedValue = converter.ConvertFrom(smallDouble.ToString());
        Console.WriteLine(convertedValue);
    }
}

给出以下错误

sh-4.3# mono main.exe                                                                                                                                                                                                                                  
-1.79769313486232E+308                                                                                                                                                                                                                                 

Unhandled Exception:                                                                                                                                                                                                                                   
System.Exception: -1.79769313486232E+308 is not a valid value for Double. ---> System.OverflowException: Number overflow.                                                                                                                              
  at System.Double.Parse (System.String s, NumberStyles style, IFormatProvider provider) [0x00000] in <filename unknown>:0                                                                                                                             
  at System.ComponentModel.DoubleConverter.ConvertFromString (System.String value, System.Globalization.NumberFormatInfo format) [0x00000] in <filename unknown>:0                                                                                     
  at System.ComponentModel.BaseNumberConverter.ConvertFrom (ITypeDescriptorContext context, System.Globalization.CultureInfo culture, System.Object value) [0x00000] in <filename unknown>:0                                                           
  --- End of inner exception stack trace ---                                                                                                                                                                                                           
  at System.ComponentModel.BaseNumberConverter.ConvertFrom (ITypeDescriptorContext context, System.Globalization.CultureInfo culture, System.Object value) [0x00000] in <filename unknown>:0                                                           
  at System.ComponentModel.TypeConverter.ConvertFrom (System.Object o) [0x00000] in <filename unknown>:0                                                                                                                                               
  at Program.Main () [0x00000] in <filename unknown>:0                                                                                                                                                                                                 
[ERROR] FATAL UNHANDLED EXCEPTION: System.Exception: -1.79769313486232E+308 is not a valid value for Double. ---> System.OverflowException: Number overflow.                                                                                           
  at System.Double.Parse (System.String s, NumberStyles style, IFormatProvider provider) [0x00000] in <filename unknown>:0                                                                                                                             
  at System.ComponentModel.DoubleConverter.ConvertFromString (System.String value, System.Globalization.NumberFormatInfo format) [0x00000] in <filename unknown>:0                                                                                     
  at System.ComponentModel.BaseNumberConverter.ConvertFrom (ITypeDescriptorContext context, System.Globalization.CultureInfo culture, System.Object value) [0x00000] in <filename unknown>:0

这是一个错误还是我错过了什么？这是在序列化测试中提出的。

Answer 1

您的解析失败，因为转换后的字符串值double.MinValue并不完全是假设的。它越来越圆了。使用：

 var convertedValue = converter.ConvertFrom(smallDouble.ToString("r"));

请参阅：The round-trip ("R") format specifier

  

往返（“R”）格式说明符用于确保数字   转换为字符串的值将被解析回相同的值   数值。此格式仅支持Single，Double，   和BigInteger类型。