Csharp/C Sharp/Generics/Generic Class

A Generic Class with Two Type Parameters

<source lang="csharp"> using System; class MyGenericClass<T, V> {

 T ob1;
 V ob2;
 public MyGenericClass(T o1, V o2) {
   ob1 = o1;
   ob2 = o2;
 }
 public void showTypes() {
   Console.WriteLine("Type of T is " + typeof(T));
   Console.WriteLine("Type of V is " + typeof(V));
 }
 public T getob1() {
   return ob1;
 }
 public V getob2() {
   return ob2;
 }

} public class Test {

 public static void Main() {
   MyGenericClass<int, string> obj = new MyGenericClass<int, string>(1, "string");
   obj.showTypes();
   int v = obj.getob1();
   Console.WriteLine("value: " + v);
   string str = obj.getob2();
   Console.WriteLine("value: " + str);
 }

}

      </source>

A simple generic class

<source lang="csharp"> using System; class MyGenericClass<T> {

 T ob;
 public MyGenericClass(T o) {
   ob = o;
 }
 public T getob() {
   return ob;
 }
 public void showType() {
   Console.WriteLine("Type of T is " + typeof(T));
 }

} public class Test {

 public static void Main() {
   MyGenericClass<int> iOb;
   iOb = new MyGenericClass<int>(102);
   iOb.showType();
   int v = iOb.getob();
   Console.WriteLine("value: " + v);
   MyGenericClass<string> strOb = new MyGenericClass<string>("Generics add power.");
   strOb.showType();
   
   string str = strOb.getob();
   Console.WriteLine("value: " + str);
 }

}

      </source>

Comparing Instances of a Type Parameter

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

 public int val;
 public MyClass(int x) { 
   val = x; 
 }
 public int CompareTo(object obj) {
   return val - ((MyClass) obj).val;
 }

} class CompareDemo {

 public static bool contains<T>(T what, T[] obs) where T : IComparable {
   foreach(T v in obs)
     if(v.rupareTo(what) == 0)
       return true;
   return false;
 }
 public static void Main() {
   int[] nums = { 1, 2, 3, 4, 5 };
   if(contains(2, nums))
     Console.WriteLine("2 is found.");
   string[] strs = { "one", "two", "three"};
   if(contains("two", strs))
     Console.WriteLine("two is found.");
   MyClass[] mcs = { new MyClass(1), new MyClass(2),
                     new MyClass(3), new MyClass(4) };
   if(contains(new MyClass(3), mcs))
     Console.WriteLine("MyClass(3) is found.");
 }

}

      </source>

Create relationship between two type parameters

<source lang="csharp"> using System; class A { } class B : A { } // Here, V must inherit T. class Gen<T, V> where V : T { } class Test {

 public static void Main() {
   // This declaration is OK because B inherits A.
   Gen<A, B> x = new Gen<A, B>();
   // This declaration is in error because
   // A does not inherit B.

// Gen<B, A> y = new Gen<B, A>();

 }

}

      </source>

Demonstrate the default keyword

<source lang="csharp"> using System; class MyClass { } class Test<T> {

 public T obj;
 public Test() {
   obj = default(T);
 }

} class DefaultDemo {

 public static void Main() {
   Test<MyClass> x = new Test<MyClass>();
   if(x.obj == null)
     Console.WriteLine("x.obj is null.");
   Test<int> y = new Test<int>();
   if(y.obj == 0)
     Console.WriteLine("y.obj is 0.");
 }

}

      </source>

Generic class with interface

<source lang="csharp"> using System; using System.Collections.Generic; public interface IShape {

   double Area {
       get;
   }

} public class Circle : IShape {

   public Circle( double radius ) {
       this.radius = radius;
   }
   public double Area {
       get {
           return 3.14 * radius * radius;
       }
   }
   private double radius;

} public class Rect : IShape {

   public Rect( double width, double height ) {
       this.width = width;
       this.height = height;
   }
   public double Area {
       get {
           return width*height;
       }
   }
   private double width;
   private double height;

} public class Shapes<T>

   where T: IShape

{

   public double TotalArea {
       get {
           double acc = 0;
           foreach( T shape in shapes ) {
               acc += shape.Area;
           }
           return acc;
       }
   }
   public void Add( T shape ) {
       shapes.Add( shape );
   }
   private List<T> shapes = new List<T>();

} public class Test {

   static void Main() {
       Shapes<IShape> shapes = new Shapes<IShape>();
       shapes.Add( new Circle(3) );
       shapes.Add( new Rect(7, 5) );
       Console.WriteLine( "Total Area: {0}", shapes.TotalArea );
   }

}

      </source>

Generic Fields

<source lang="csharp">

using System; using System.Collections.Generic; using System.Text; class MyType<T, U> {

   private T _myFirstDataMember;
   private U _mySecondDataMember;
   public MyType(T val1, U val2) {
       this._myFirstDataMember = val1;
       this._mySecondDataMember = val2;
   }
   public T GetFirstDataMember() {
       return this._myFirstDataMember;
   }
   public U GetSecondDataMember() {
       return this._mySecondDataMember;
   }

} class MyApp {

   static void main(String[] args) {
       MyType<string, string> testType = new MyType<string, string>("Val1", "Val2");
       Console.WriteLine(testType.GetFirstDataMember());
       Console.WriteLine(testType.GetSecondDataMember());
   }

}

      </source>

"This" Reference for Generic Types

<source lang="csharp">

   using System;
   public class Starter{
       public static void Main(){
           MyGenericClass<int> obj=new MyGenericClass<int>();
           obj.MethodA();
       }
   }
   
   class MyGenericClass<T> {
       public T MethodA() {
          T var=default(T);
          Console.WriteLine(this.GetType().ToString());
          return var;
       }
   }
          
      </source>