Csharp/CSharp Tutorial/Class/IFormattable

Formattable Vector

<source lang="csharp">using System; using System.Collections.Generic; using System.Text; using System.Text;

class MainEntryPoint {

   static void Main() {
       Vector v1 = new Vector(1, 32, 5);
       Vector v2 = new Vector(845.4, 54.3, -7.8);
       Console.WriteLine("{0,30:IJK}   \n   {1,30:IJK} \n", v1, v2);
       Console.WriteLine("{0,30}       \n   {1,30} \n", v1, v2);
       Console.WriteLine("{0,30:VE}    \n   {1,30:VE} \n", v1, v2);
       Console.WriteLine("{0,20:N}     \n   {1,20:N}", v1, v2);
   }

} struct Vector : IFormattable {

   public double x, y, z;
   public Vector(double x, double y, double z) {
       this.x = x;
       this.y = y;
       this.z = z;
   }
   public string ToString(string format, IFormatProvider formatProvider) {
       if (format == null)
           return ToString();
       string formatUpper = format.ToUpper();
       switch (formatUpper) {
           case "N":
               return "|| " + Norm().ToString() + " ||";
           case "VE":
               return String.Format("( {0:E}, {1:E}, {2:E} )", x, y, z);
           case "IJK":
               StringBuilder sb = new StringBuilder(x.ToString(), 30);
               sb.Append(" i + ");
               sb.Append(y.ToString());
               sb.Append(" j + ");
               sb.Append(z.ToString());
               sb.Append(" k");
               return sb.ToString();
           default:
               return ToString();
       }
   }
   public Vector(Vector rhs) {
       x = rhs.x;
       y = rhs.y;
       z = rhs.z;
   }
   public override string ToString() {
       return "( " + x + " , " + y + " , " + z + " )";
   }
   public double this[uint i] {
       get {
           switch (i) {
               case 0:
                   return x;
               case 1:
                   return y;
               case 2:
                   return z;
               default:
                   throw new IndexOutOfRangeException(
                      "Attempt to retrieve Vector element" + i);
           }
       }
       set {
           switch (i) {
               case 0:
                   x = value;
                   break;
               case 1:
                   y = value;
                   break;
               case 2:
                   z = value;
                   break;
               default:
                   throw new IndexOutOfRangeException(
                      "Attempt to set Vector element" + i);
           }
       }
   }
   private const double Epsilon = 0.0000001;
   public static bool operator ==(Vector lhs, Vector rhs) {
       if (System.Math.Abs(lhs.x - rhs.x) < Epsilon &&
          System.Math.Abs(lhs.y - rhs.y) < Epsilon &&
          System.Math.Abs(lhs.z - rhs.z) < Epsilon)
           return true;
       else
           return false;
   }
   public static bool operator !=(Vector lhs, Vector rhs) {
       return !(lhs == rhs);
   }
   public static Vector operator +(Vector lhs, Vector rhs) {
       Vector Result = new Vector(lhs);
       Result.x += rhs.x;
       Result.y += rhs.y;
       Result.z += rhs.z;
       return Result;
   }
   public static Vector operator *(double lhs, Vector rhs) {
       return new Vector(lhs * rhs.x, lhs * rhs.y, lhs * rhs.z);
   }
   public static Vector operator *(Vector lhs, double rhs) {
       return rhs * lhs;
   }
   public static double operator *(Vector lhs, Vector rhs) {
       return lhs.x * rhs.x + lhs.y + rhs.y + lhs.z * rhs.z;
   }
   public double Norm() {
       return x * x + y * y + z * z;
   }

}</source>

Implementation of IFormattable

<source lang="csharp">using System; public class MyClass : IFormattable {

   private string title;
   private string[] names;
   public MyClass(string title, params string[] names)
   {
       this.title = title;
       this.names = names;
   }
   public override string ToString()
   {
       return ToString("G", null);
   }
   public string ToString(string format, IFormatProvider formatProvider)
   {
       string result = null;
       if (format == null) 
           format = "G";
       switch (format.ToUpper()[0])
       {
           case "S":
               result = "S." ;
               break;
           case "P":
               result = "P. ";
               break;
           case "I":
               result = "I. ";
               break;
           case "G":
           default:
               result = "G. ";
               break;
       }
       return result;
   }

} public class MainClass {

   public static void Main()
   {
       MyClass person = new MyClass("Mr", "A", "B", "C", "D");
       System.Console.WriteLine("Dear {0:G},", person);
       System.Console.WriteLine("Dear {0:P},", person);
       System.Console.WriteLine("Dear {0:I},", person);
       System.Console.WriteLine("Dear {0},", person);
       System.Console.WriteLine("Dear {0:S},", person);
   }

}</source>

Dear G. ,
Dear P. ,
Dear I. ,
Dear G. ,
Dear S.,

Implements IFormattable with switch statement

<source lang="csharp">using System;

public class Employee : IFormattable {

   private string title;
   private string[] names;
   public Employee(string title, params string[] names) {
       this.title = title;
       this.names = names;
   }
   public override string ToString() {
       return ToString("G", null);
   }
   public string ToString(string format, IFormatProvider formatProvider) {
       string result = null;
       if (format == null) format = "G";
       switch (format.ToUpper()[0]) {
           case "S":
               result = names[0][0] + "." + names[names.Length - 1];
               break;
           case "P":
               if (title != null && title.Length != 0) {
                   result = title + ".";
               }
               break;
           case "I":
               result = names[0];
               break;
           case "G":
           default:
               result = names[0] + " " + names[names.Length - 1];
               break;
       }
       return result;
   }

} public class MainClass {

   public static void Main() {
       Employee person = new Employee("Mr", "A", "B", "C", "D");
       System.Console.WriteLine("{0:G},", person);
       System.Console.WriteLine("{0:P},", person);
       System.Console.WriteLine("{0:I},", person);
       System.Console.WriteLine("{0},", person);
       System.Console.WriteLine("{0:S},", person);
   }

}</source>