C＃将20位精度双精度转换为字符串并再次返回 [英] C# Converting 20 digit precision double to string and back again

问题描述

在C＃中。我有一个双数字（我从数据库中提取），具有20位精度。在Visual Studio（使用QuickWatch）中，我可以看到double的值为= 0.00034101243963859839。

In C#. I have a double (which I've extracted from a database) that has 20 digit precision. In Visual Studio (using QuickWatch) I can see the value of the double to be = 0.00034101243963859839.

我想在文本框中显示该值，然后将其设置为当我把它拿出来把它转换成一个双倍的同样的价值。但我总是丢失最后两位数字

I want to display this value in a textbox and then have it be the same value when I take it out and convert it back into a double. But I always lose the last two digits

我已经尝试了以下内容：

I've tried the following:

double d = 0.00034101243963859839;
string s = d.ToString();
string s2 = d.ToString("F20");
string s3 = d.ToString("0.00000000000000000000"); -- 20 0's
string s4 = (d*100d).ToString();

在这些情况下：

s  = 0.000341012439638598
s2 = 0.00034101243963859800
s3 = 0.00034101243963859800
s4 = 0.0341012439638598

我想要能够做以下：

double d = 0.00034101243963859839;
string s = d.ToString();
//...
double d2 = double.Parse(s);
if(d == d2)
{
  //-- Success
}

有没有办法保留最后两位数的精度？

Is there any way to keep those last two digits of precision??

推荐答案

使用R数字格式字符串：

double d = 0.00034101243963859839;
string s = d.ToString("R");
//...
double d2 = double.Parse(s);
if(d == d2)
{
  //-- Success
}

R 代表往返。从链接的文档：

The R stands for "round-trip". From the linked document:

此格式仅适用于单和双类型。往返说明符保证转换为字符串的数值将被解析为相同的数值。

This format is supported only for the Single and Double types. The round-trip specifier guarantees that a numeric value converted to a string will be parsed back into the same numeric value.

我怀疑没有办法保留最后两位数字。只有这么多精度可用，我怀疑他们首先将它们变成 d 。但是您可以确保您的字符串至少读取您所做的正确。

As an aside, I suspect there is no way to keep those last two digits. There's only so much precision available, and I doubt they ever make it into d in the first place. But you can make sure your string at least reads back what you do have correctly.

如果您真的需要额外的精度，可以尝试使用十进制。

If you really need the additional precision, you might try using a decimal instead.

这篇关于C＃将20位精度双精度转换为字符串并再次返回的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！