One significant figure in C#

[mrshrinkray@googlemail.com]

I feel a bit ashamed asking this after 6 years of C#, but is there a
format string for significant figures before the decimal place?

e.g.
2,354,856:
1 sf = 2,000,000
2 sf = 2,400,000
3 sf = 2,350,000

{0:G} or g gives me scientific notation, but I'm after the above.

Thanks

[Dave Shooter]

Re: One significant figure in C#

<mrshrinkray@go oglemail.comwro te in message
news:9b2430fc-810e-4d39-bafe-4e68dde53d4d@a1 g2000hsb.google groups.com...

>I feel a bit ashamed asking this after 6 years of C#, but is there a
format string for significant figures before the decimal place?
>
e.g.
2,354,856:
1 sf = 2,000,000
2 sf = 2,400,000
3 sf = 2,350,000
>
{0:G} or g gives me scientific notation, but I'm after the above.

The following doesn't fully answer your question but might help, it's a
customer formatter I've cobbled together based on the code at:

http://msdn.microsoft.com/en-us/libr...tprovider.aspx.

I believe the rounding need to be implemented in the
SFFormatProvide r.Format() method to achieve the exact results you're looking
for but this shouldn't be too difficult.

class Program
{
static void Main(string[] args)
{
int val = 2354856;
Console.WriteLi ne(String.Forma t(
new SFFormatProvide r(), "{0}", val));
Console.WriteLi ne(String.Forma t(
new SFFormatProvide r(), "{0:1}", val));
Console.WriteLi ne(String.Forma t(
new SFFormatProvide r(), "{0:2}", val));
Console.WriteLi ne(String.Forma t(
new SFFormatProvide r(), "{0:3}", val));
}
}

public class SFFormatProvide r : IFormatProvider , ICustomFormatte r
{
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomF ormatter))
return this;
else
return null;
}

public string Format(string format, object arg,
IFormatProvider formatProvider)
{
char[] carr = arg.ToString(). ToCharArray();
int digits = 1;
if (!String.IsNull OrEmpty(format) )
digits = Int32.Parse(for mat);

for (int i = digits; i < carr.Length; i++)
{
carr[i] = '0';
}
return String.Format(" {0:n0}",
Convert.ToInt32 (new String(carr)));
}
}

Regards
David

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Re: One significant figure in C#

mrshrinkray@goo glemail.com wrote:

I feel a bit ashamed asking this after 6 years of C#, but is there a
format string for significant figures before the decimal place?
>
e.g.
2,354,856:
1 sf = 2,000,000
2 sf = 2,400,000
3 sf = 2,350,000
>
{0:G} or g gives me scientific notation, but I'm after the above.

I don't think so.

You will need to code it yourself.

One way:

public static string SpecialFormat(i nt v, int sf)
{
int k = (int)Math.Pow(1 0, (int)(Math.Log1 0(v) + 1 - sf));
int v2 = ((v + k/2) / k) * k;
return v2.ToString("0, 0");
}

(the calculation of k can be optimized if speed is critical)

Arne