Csharp/CSharp Tutorial/Class/ICustomFormatter

ICustomFormatter IFormatProvider

/*
Quote from
Accelerated C# 2005
# By Trey Nash
# ISBN: 1-59059-717-6
# 432 pp.
# Published: Aug 2006
*/
using System;
using System.Text;
using System.Globalization;
public class ComplexDbgFormatter : ICustomFormatter, IFormatProvider
{
    public object GetFormat( Type formatType ) {
        if( formatType == typeof(ICustomFormatter) ) {
            return this;
        } else {
            return CultureInfo.CurrentCulture.
                GetFormat( formatType );
        }
    }
    public string Format( string format, object arg, IFormatProvider formatProvider ) {
        if( arg.GetType() == typeof(Complex) && format == "DBG" ) {
            Complex cpx = (Complex) arg;
            StringBuilder sb = new StringBuilder();
            sb.Append( arg.GetType().ToString() + " " );
            sb.AppendFormat( "Real:{0} ", cpx.Real );
            sb.AppendFormat( "Img: {0} ", cpx.Img );
            return sb.ToString();
        } else {
            IFormattable formatable = arg as IFormattable;
            if( formatable != null ) {
                return formatable.ToString( format, formatProvider );
            } else {
                return arg.ToString();
            }
        }
    }
}
public struct Complex : IFormattable
{
    public Complex( double Real, double Img ) {
        this.Real = Real;
        this.Img = Img;
    }
    public string ToString( string format, IFormatProvider formatProvider ) {
        StringBuilder sb = new StringBuilder();
        sb.Append( "( " + Real.ToString(format, formatProvider) );
        sb.Append( " : " + Img.ToString(format, formatProvider) );
        sb.Append( " )" );
        return sb.ToString();
    }
    public double Real;
    public double Img;
}
public class MainClass
{
    static void Main() {
        CultureInfo local = CultureInfo.CurrentCulture;
        CultureInfo germany = new CultureInfo( "de-DE" );
        Complex cpx = new Complex( 12.3456, 1234.56 );
        string strCpx = cpx.ToString( "F", local );
        Console.WriteLine( strCpx );
        strCpx = cpx.ToString( "F", germany );
        Console.WriteLine( strCpx );
        ComplexDbgFormatter dbgFormatter = new ComplexDbgFormatter();
        strCpx = String.Format( dbgFormatter,"{0:DBG}",  cpx );
        Console.WriteLine( "\nDebugging output:\n{0}", strCpx );
    }
}

( 12.35 : 1234.56 )
( 12,35 : 1234,56 )
Debugging output:
Complex Real:12.3456 Img: 1234.56