IFormatProvider从double到string的科学转换

IFormatProvider从double到string的科学转换 - 位数(IFormatProvider scientific conversion from double to string - number of digits)

我有从double到string的转换问题。

我要转换：

double值：0.0772486324655191

字符串值：0.0772486324655191

如果长度大于小数点后的16位数，我希望它像这样：

double值：0.00063500244832493823

字符串值：6.3500244832493823e-004

我试图用IFormatProvider模式转换它：

0.0000000000000000e000

但第一种情况的结果是

7.7248632465519100e-002

如何获取双向量中的位数？ 或者更好：我应该如何正确使用格式提供程序？

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

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));

最满意答案

为此，您肯定需要创建自定义格式化程序。

要创建自定义格式化程序，您应该知道： string.Format具有以下重载： string.Format(IFormatProvider, string, object[]) ，因此您必须创建一个“提供” ICustomFormatter的IFormatProvider ，它将处理您的自定义格式。 两个接口都可以轻松使用相同的类。

这里有一些代码完全符合您的描述：

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); } } }

以下是如何使用此代码的示例：

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); }

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); }