String format from double C#

Question

I have double for example 1.890. How I can format like this:

• if it is 100 must be 18.90
• if it is 10000 must be 0.1890
• if it is 100000 must be 0.01890
• if it is 10 must be 189.0
• if it is 1 must be 1890

I tried this:

switch (price)
        {
            case (int)scales.zero:
                format = "{0:0}";
                break;
            case (int)scales.one:
                format = "{0:0}";
                break;
            case (int)scales.two:
                format = "{0:000}";
                break;
            case (int)scales.three:
                format = "{0:0000}";
                break;
            case (int)scales.four:
                format = "{0:00000}";
                break;
            case (int)scales.five:
                format = "{0:00000}";
                break;
            default:
                format = "{0:0.00}";
                break;
        }

        if (!string.IsNullOrWhiteSpace(format))
            res = string.Format(format, value);
        return res;

Answer 1

Your default clause includes a dot: {0:0.00}. Do it like that in the other cases: {0:0.00000} to have 5 zeroes. And divide the number by 100, 1000, etc. before formatting.

Answer 2

First of all, your results are little bit strange, honestly. For example; other than 1 case, all results have decimal separator but for 1 case, it doesn't have any thousand separator. It is okey to solve this but seems strange to me.

Second, I think your double is 1890 rather than 1.890 because when you use your enum values, looks like they divide your double value with their values with powered 10 .

If so, let's define your enum value first.

enum scales
{
    zero = 1,
    one = 10,
    two = 100,
    three = 1000,
    four = 10000,
    five = 100000
}

And second, create a culture that has . as a decimal separator and has empty string as a thousand separator. For this, let's Clone a InvariantCulture and set it's NumberGroupSeparator to empty string.

var culture = (CultureInfo)CultureInfo.InvariantCulture.Clone();
culture.NumberFormat.NumberGroupSeparator = string.Empty;

Then we can use that culture to format our results using "N" format specifier and proper precision, after we divide our double value with the enum values that mathes.

double d = 1890;
int price = 1;
string result = "";
switch (price)
{
    case (int)scales.zero:
         d = d / (int)scales.zero;
         result = d.ToString(culture);
         break;
    case (int)scales.one:
         d = d / (int)scales.one;
         result = d.ToString("N1", culture);
         break;
    case (int)scales.two:
         d = d / (int)scales.two;
         result = d.ToString("N2", culture);
         break;
    case (int)scales.three:
         d = d / (int)scales.three;
         result = d.ToString("N3", culture);
         break;
    case (int)scales.four:
         d = d / (int)scales.four;
         result = d.ToString("N4", culture);
         break;
    case (int)scales.five:
         d = d / (int)scales.five;
         result = d.ToString("N5", culture);
         break;
    default:
         break;
}

Console.WriteLine(result); 

You can change the value of price to 10 , 100 , 1000 , 10000 , 100000 and this will be generate exactly what results do you want.