C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace TestDerivation
{
  class Program
  {
    static void Main(string[] args)
    {
      List<BaseClass> list = new List<BaseClass>();
      list.Add(new BaseClass { Id = 1 });
      list.Add(new Derived { Id = 2, Name = "Jammer" });
      foreach (BaseClass item in list)
      {
        if (item is Derived)
        {
          Derived derived = item as Derived;
          Console.WriteLine("{0} {1}", derived.Id, derived.Name);
        }
        else
        {
          Console.WriteLine("{0}", item.Id);
        }
      }
      Console.Read();
    }
  }
  public class BaseClass
  {
    public int Id { get; set; }
  }
  public class Derived : BaseClass
  {
    public string Name { get; set; }
  }
}

class BaseClass {
   public int value1;
}
class DerivedClass : BaseClass {
   public int value2;
}

static void Main() {
   DerivedClass dc = new DerivedClass();
   BaseClass bc = dc; //works

   BaseClass bc2 = new BaseClass();
   DerivedClass dc2 = (DerivedClass)bc2; //fails at runtime because BaseClass doesn't have all the functionality of the DerivedClass
}

rahul21 wrote:

Inside the selected index changed event of combobox I write this line of code:-

rahul21 wrote:

I am using connected architecture.

If your application is intended for international use with a variety of keyboards, the use of Send could yield unpredictable results and should be avoided

Blumen wrote:

new protected member declared in sealed class

I dont use any unmanaged objects, so I need to dispose only connection and command object in this class. Could anyone help me with this error?

Blumen wrote:

But dispose is a method of base class, so is it okay to remove the virtual keyword?

Blumen wrote:

Does that mean I have to override dispose on my class

Blumen wrote:

and make class sealed

Blumen wrote:

ObjectDatasource control in ADO.NET 2.0. So will this control call my class's Dispose()

public class CustomerDal
{
  public void AddCustomer(...){
     using(SqlConnection connection = new SqlConnection(...))
     using(SqlCommand command = new SqlCommand(connection,...)){
        // your code
     }
  }
}

Pete O'Hanlon wrote:

They give broad brush guidelines that people tend to end up as treating as gospel.