IFormatProvider从double到string - 数字数字的科学转换 [英] IFormatProvider scientific conversion from double to string - number of digits

问题描述

我想转换：

双重值：0.0772486324655191

字符串值：0.0772486324655191

如果长度大于小数点后的16位数，我想要这样：

double value：0.00063500244832493823

字符串值：6.3500244832493823e-004

我已尝试将其转换为IFormatProvider模式：

0.0000000000000000e000

但是，第一种情况的结果是

7.7248632465519100e-002

我如何获取我的双向量中的数字位数？或者更好：如何正确使用格式提供程序？

 字符串说明符;文化文化; 
 specifier =0.0000000000000000e000; 
 culture = CultureInfo.CreateSpecificCulture（en-US）; 
 Console.WriteLine（DoubleMirrored [0] .ToString（specifier，CultureInfo.InvariantCulture））; 
  

解决方案

为此，您绝对需要创建一个自定义格式化。

要创建自定义格式化程序，您应该了解以下内容：

string.Format 有以下重载： string.Format（IFormatProvider，string，object []），所以你必须创建一个 IFormatProvider 这将提供一个 ICustomFormatter ，它将处理您的自定义格式。

这里有一些代码完全符合您的描述：

  public class DoubleFormatter：IFormatProvider，ICustomFormatter 
 {
 //实现IFormatProvider：
 public object GetFormat（Type t）{
 if（ t == typeof（ICustomFormatter））{
 return this; 
} 
返回null; 
} 
 //实现ICustomFormatter：
 public string Format（string format，object arg，IFormatProvider provider）{
 //搜索自定义的EE格式说明符：
 if（format == null ||！format.StartsWith（EE））return null; 
 format = format.Substring（2）; //修剪EE
 //确定截止前有多少个数字：
 int数字; 
 if（！int.TryParse（format，out digits））{
 throw new FormatException（Format must contain digits）; 
} 
 
 //获取值：（注意，这将适用于任何数字类型）
 var value = Convert.ToDouble（arg）; 
 //转换为字符串而不使用指数格式：
 var output = value.ToString（0+（new string（'＃'，digits）），provider）; 
 //确定显示的数字是多少（这部分不兼容文化）
 var length = output.Length  -  output.IndexOf（。）; 
 if（length< = digits）{
 return output; 
} else {
 return value.ToString（E+ format，provider）; 
} 
} 
} 
  

这里是一个例子使用以下代码：

  var tests = new [] {
 0.0000055555，
 0.00000555555555555555555，
}; 
 
 var formatter = new DoubleFormatter（）; 
 foreach（var t in tests）{
 var result = string.Format（formatter，{0：EE15}，t）; 
 Console.WriteLine（result）; 
} 
  

I have a problem with the conversion from double to string.

I want to convert:

double value: 0.0772486324655191

string value: 0.0772486324655191

and if the length is bigger than 16 digits after the decimal point I want it like this:

double value: 0.00063500244832493823

string value: 6.3500244832493823e-004

I have tried to convert it with IFormatProvider Pattern:

0.0000000000000000e000

But the result in the first case is

7.7248632465519100e-002

How can I get the number of digits in my double vector? Or better: how should I use the format provider correctly?

String specifier;
CultureInfo culture;
specifier = "0.0000000000000000e000";
culture = CultureInfo.CreateSpecificCulture("en-US");
Console.WriteLine(DoubleMirrored[0].ToString(specifier, CultureInfo.InvariantCulture));

解决方案

To do this, you definitely need to create a custom formatter.

To create a custom formatter, here's what you should know:
string.Format has the following overload: string.Format(IFormatProvider, string, object[]), so you must create a IFormatProvider that will "provide" a ICustomFormatter, which will handle your custom formatting. The same class can be easily used for both interfaces.

Here's some code that does exactly what you describe:

public class DoubleFormatter : IFormatProvider, ICustomFormatter 
{
    // Implementation of IFormatProvider:
    public object GetFormat(Type t) {
        if (t == typeof(ICustomFormatter)) {
            return this;
        }
        return null;
    }
    // Implementation of ICustomFormatter:
    public string Format(string format, object arg, IFormatProvider provider) {
        // Search for the custom "EE" format specifier:
        if (format == null || !format.StartsWith("EE")) return null;
        format = format.Substring(2); // Trim "EE"
        // Determine how many digits before we cutoff:
        int digits;
        if (!int.TryParse(format, out digits)) {
            throw new FormatException("Format must contain digits");
        }

        // Get the value: (note, this will work for any numeric type)
        var value = Convert.ToDouble(arg);
        // Convert to string without using Exponential format:
        var output = value.ToString("0."+(new string('#',digits)), provider);
        // Determine how many digits are showing: (this part isn't culture-compatible)
        var length = output.Length - output.IndexOf(".");
        if (length <= digits) {
            return output;
        } else {
            return value.ToString("E"+format, provider);
        }
    }
}

And here's an example of how to use this code:

var tests = new[]{
    0.0000055555,
    0.00000555555555555555555,
};

var formatter = new DoubleFormatter();
foreach (var t in tests){ 
    var result = string.Format(formatter, "{0:EE15}", t);
    Console.WriteLine(result);
}

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