C# How to format a double to one decimal place without rounding

Question

I need to format a double value to one decimal place without it rounding.

double value = 3.984568438706
string result = \"\";

What I have tried

Answer 1

I would make a utility method to handle this:

static double Truncate(double value, int digits)
{
    double mult = System.Math.Pow(10.0, digits);
    return System.Math.Truncate(value * mult) / mult;
}

You could then do:

result = Truncate(value, 1).ToString("##.#", System.Globalization.CultureInfo.InvariantCulture) + "%"; 

Note that you may also want Math.Floor instead of truncate - but it depends on how you want negative values handled.