Use an interface constraint : Generic Constraint « Generics « C# / C Sharp

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C# / C Sharp » Generics » Generic ConstraintScreenshots 
Use an interface constraint
Use an interface constraint


using System;

class NotFoundException : ApplicationException { }

public interface IPhoneNumber {
  string Number {
    get;
    set;
  }

  string Name {
    get;
    set;
  }
}

class Friend : IPhoneNumber {
  string name;
  string number;

  public Friend(string n, string num) {
    name = n;
    number = num;
  }

  public string Number {
    get return number; }
    set number = value; }
  }

  public string Name {
    get return name; }
    set name = value; }
  }
}

class Supplier : IPhoneNumber {
  string name;
  string number;

  public Supplier(string n, string num) {
    name = n;
    number = num;
  }
  public string Number {
    get return number; }
    set number = value; }
  }

  public string Name {
    get return name; }
    set name = value; }
  }
}

class EmailFriend {
}

class PhoneList<T> where T : IPhoneNumber {
  T[] phList;
  int end;

  public PhoneList() {
    phList = new T[10];
    end 0;
  }

  public bool add(T newEntry) {
    if(end == 10return false;

    phList[end= newEntry;
    end++;

    return true;
  }

  public T findByName(string name) {

    for(int i=0; i<end; i++) {

      if(phList[i].Name == name)
        return phList[i];

    }
    throw new NotFoundException();
  }
  public T findByNumber(string number) {

    for(int i=0; i<end; i++) {
      if(phList[i].Number == number)
        return phList[i];
    }
    throw new NotFoundException();
  }
}

class Test {
  public static void Main() {

    PhoneList<Friend> plist = new PhoneList<Friend>();
    plist.add(new Friend("A""555-1111"));
    plist.add(new Friend("B""555-6666"));
    plist.add(new Friend("C""555-9999"));

    try {
      Friend frnd = plist.findByName("B");

      Console.Write(frnd.Name + ": " + frnd.Number);

    catch(NotFoundException) {
      Console.WriteLine("Not Found");
    }

    Console.WriteLine();

    PhoneList<Supplier> plist2 = new PhoneList<Supplier>();
    plist2.add(new Supplier("D""555-4444"));
    plist2.add(new Supplier("E""555-3333"));
    plist2.add(new Supplier("F""555-2222"));

    try {
      Supplier sp = plist2.findByNumber("555-2222");
      Console.WriteLine(sp.Name + ": " + sp.Number);
    catch(NotFoundException) {
        Console.WriteLine("Not Found");
    }

    //PhoneList<EmailFriend> plist3 = new PhoneList<EmailFriend>(); 
  }
}
           
       
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5.Reference Type Constraint: A reference type constraint restricts a type parameter to a reference type.
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8.A type parameter can be used as a constraintA type parameter can be used as a constraint
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