Convert string to double, but the first character is a dot-CodePudding

I need to convert a string value similar to .904 and -.904 to a double. I haven't found any simple and direct way to do so, except to copy each character to another string and manually add the zero and then covert to double.

CodePudding user response：

Just make sure to specify a culture that supports that format when trying to convert from string to double, for example the culture-independent format CultureInfo.InvariantCulture.

using System;
using System.Globalization;
                    
public class Program
{
    public static void Main()
    {
        HandleSource("-.904");
        HandleSource(".904");
    }
    
    public static void HandleSource(string src)
    {
        double d = Double.Parse(src, CultureInfo.InvariantCulture);
        Console.WriteLine(d);
    }
}

https://dotnetfiddle.net/ftlYFE

When you don't specify an explicit culture and get the "Input string was not in a correct format" exception, this is because you run the code in an environment with a culture that uses comma as decimal separator.

CodePudding user response：

You can convert with the help of Convert.ToDouble function.

The small demo link I am attaching for your reference.

CodePudding user response：

I think this is the simplest way: https://dotnetfiddle.net/94UV1n

public static void Main()
{
    var s = "-.123";
    if (s[0]=='-') {
        Console.WriteLine(-double.Parse("0" s.Substring(1)));
    } else {
        Console.WriteLine(double.Parse("0" s));
    }
}