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Attributes

Attributes allow you to add declarative information to your programs. This information can then be queried at runtime using reflection

There are several Pre-defined attributes provided by .NET.It is also possible to create your own Custom Attributes.

A few pre-defined attributes with in the .NET framework.
obsolete    – Marks types and type members outdated
WebMethod  – To expose a method as an XML Web service method
Serializable  – Indicates that a class can be serialized


It is possible to customize the attributes using parameters
An attributes is a class that inherits from SYSTEM.ATTRIBUTES base class.
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using System;
using System.Collections.Generic;

namespace ConsoleApplication4
{
    public class MainClass
    {
        private static void Main()
        {
            Calculator.AddNumber(new List<int>() {10,20, 30});
           

        }
    }

    public class Calculator
    {
        [Obsolete(“Use(List<int> Numbers)Method”,true)]
        public static int AddNumber(int FirstNumber, int SecondNumber)
        {
            return FirstNumber + SecondNumber;
        }

        public static int AddNumber(List<int> Numbers)
        {
            int Sum = 0;
            foreach (int Number in Numbers)
            {
                Sum = Sum + Number;
            }
            return Sum;
        }
    }

}

ACCESS MODIFIERS IN C#

Types Vs Type Members


In C# there are 5 different access modifiers in c#
1.Private
2.Protected
3.Internal
4. Protected Internal
5. Public

Private members are available only with in the containing type, where as public members are available any where. There is no restricction.

Protected Members are available, with in the containing type and to the types that derive from the containing type

Access Modifier                       Accessibility
Private ->                  Only with in the containing class
Public ->                  Any where, No Restrictions
Protected ->                 With in the containing types and the types derived from the
                                                 containing type.
————————————————————————————————————————-

using System;
using System.IO;

namespace ConsoleApplication4
{

    //public class Customer
    //{

    //    private int _id;

    //    public int Id
    //    {
    //        get { return _id; }
    //        set { _id = value; }

    //    }
    //}

    public class Customer
    {
        protected int _id;
    }

    public class corporateCustomer : Customer
    {
        public void printID()
        {
            corporateCustomer cc = new corporateCustomer();
            cc._id = 101;
        }
    }

   public  class Program
    {
        public static void Main()
    {
        Customer C1 = new Customer();
        Console.WriteLine(C1._id);
    }

    }
}
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INTERNAL AND PROTECTED INTERNAL ACCESS MODIFIERS IN C#

WHY ENUMS

Enums are strongly typed constants

If a program uses set of integral numbers, consider replacing them with enums. otherwise the program becomes less
 > Readable
 > Maintainable

———————————————————————————————————————–

using System;
using System.IO;

namespace ConsoleApplication4
{
    class Program
    {
        public static void Main()
        {
            Customer[] customers = new Customer[3];

            customers[0] = new Customer
            {
                Name = “Malla”,
                Gender = 1
            };
            customers[1] = new Customer
            {
                Name = “mary”,
                Gender = 2

            };
            customers[2] = new Customer
            {
                Name = “hyyjjj”,
                Gender = 0
            };

            foreach (Customer customer in customers)
            {
                Console.WriteLine(“Name = {0} && Gender = {1}”, customer.Name, GetGender(customer.Gender));
                Console.ReadLine();
            }

        }

        public static string GetGender(int gender)
        {
            switch(gender)
            {
//      INTEGRAL NUMBERS BESIDE CASES SHOULD BE REPLACES WITH ENUMS TO //BETTER READABLE
                case 0:
                    return “Unknown”;
                case 1:
                    return “Male”;
                case 2: 
                    return “Female”;
                default:
                    return “Invalid data detected”;
            }
    }
        //0 Unknown
        //1  Male
        //2 Female

        public class Customer
        {
            public string Name { get; set; }
            public int Gender { get; set; }
        }
    }
}
————————————————————————————————————————

USE ENUMS FOR THE ABOVE PROGRAM MORE READABLE

using System;
using System.IO;

namespace ConsoleApplication4
{
    class Program
    {
        public static void Main()
        {
            Customer[] customers = new Customer[3];

            customers[0] = new Customer
            {
                Name = “Malla”,
                Gender = Gender.Male
            };
            customers[1] = new Customer
            {
                Name = “mary”,
                Gender = Gender.Female

            };
            customers[2] = new Customer
            {
                Name = “hyyjjj”,
                Gender = Gender.Unknown
            };

            foreach (Customer customer in customers)
            {
                Console.WriteLine(“Name = {0} && Gender = {1}”, customer.Name, GetGender(customer.Gender));
                Console.ReadLine();
            }

        }

        public static string GetGender(Gender gender)
        {
            switch(gender)
            {
                case Gender.Unknown:
                    return “Unknown”;
                case Gender.Male:
                    return “Male”;
                case Gender.Female: 
                    return “Female”;
                default:
                    return “Invalid data detected”;
            }
    }
        //0 Unknown
        //1  Male
        //2 Female
        public enum Gender
        {
            Unknown,
            Male,
            Female
        };

        public class Customer
        {
            public string Name { get; set; }
            public Gender Gender { get; set; }
        }
    }
}


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ENUMS USAGE


If a program uses set of integral numbers, consider replacing them with enums. otherwise the program becomes less
 > Readable
 > Maintainable

1.Enums are enumerations
2.Enums are strongly typed constants, Hence, an explicit cast is needed to convert from enum type to an integral type and vice versa.Also an enum of one type cannot be implicitly assigned to an enum of another type even though the underlying value of their members are the same.
3. The default underlying type of an enum is int.
4.The default value for firt element is zero and gets incremently by 1.
5 it is possible to customize the underlying type and values.
6. Enums are value types.

7. Enum keyword (all small letters) is used to create enumerations. where as Enum class, contains staticGetValues() and GetNames() methods which can be used to list Enum underlying type values and Names.

Enum(with capital Eis a class)

enum (with small e is to create enumerations)