Calling base class constructor from derived class Constructor

If you want to call one constructor from another in a class itself, then use this()

If you want to call base class constructor from derived class constructor, then use base().

If you are not calling any base class constructor from derived class, then always base class default constructor will called.

Sample Program:

    static class Program

    {

        /// <summary>

        /// The main entry point for the application.

        /// </summary>

        [STAThread]

        static void Main()

        {

            DerivedClass objDerivedClass = new DerivedClass();

            //Output :  BaseClass - Default constructor

            //          DerivedClass - Default constructor

            DerivedClass objDerivedClass1 = new DerivedClass("PageId1234");

            //Output :  BaseClass - Default constructor

            //          DerivedClass - Default constructor

            //          DerivedClass - Overloaded constructor calling Default constructor using this()

            DerivedClass objDerivedClass2 = new DerivedClass(10800, "Student");

            //Output :  BaseClass - Overloaded constructor

            //          DerivedClass - Overloaded constructor calling base class constructor

            Console.ReadLine();

        }

    }

    public partial class BaseClass

    {

        int tempCommandTimeout = 0;

        /// <summary>

        /// Default constructor

        /// </summary>

        public BaseClass()

        {

           tempCommandTimeout = 300;

           Console.WriteLine("BaseClass - Default constructor");

        }

        /// <summary>

        /// Overloaded constructor to Set Command-timeout

        /// </summary>

        /// <param name="iCommandTimeout"></param>

        public BaseClass(int iCommandTimeout)

        {

            tempCommandTimeout = iCommandTimeout;

            Console.WriteLine("BaseClass - Overloaded constructor");

        }

    }

    public partial class DerivedClass : BaseClass

    {

        string TableName = "";

        string PageID = "";

        /// <summary>

        /// Default constructor

        /// </summary>

        public DerivedClass()

        {

            this.TableName = "Employee";

            Console.WriteLine("DerivedClass - Default constructor");

        }

        /// <summary>

        /// Overloaded constructor calling Default constructor using this()

        /// </summary>

        /// <param name="ePageID"></param>

        public DerivedClass(string ePageID)

            : this()

        {

            PageID = ePageID;

            Console.WriteLine("DerivedClass - Overloaded constructor calling Default constructor using this()");

        }

        /// <summary>

        /// Overloaded constructor calling base class constructor to Set Command-timeout

        /// </summary>

        /// <param name="iCommandTimeout"></param>

        public DerivedClass(int iCommandTimeout, string strTableName)

            : base(iCommandTimeout)

        {

            TableName = strTableName;

            Console.WriteLine("DerivedClass - Overloaded constructor calling base class constructor");

        }

    }