Immutable objects in C#

In this article Shivprasad koirala explain about Immutable in C#.

It covers following points:

1. Introduction
2. What are immutable objects?
3. Where are immutable objects used?
4. How can we create immutable objects in C#?

Read Full Article: Click here.

Jay Ganesh !!!!!

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OOPS – Polymorphism and Inheritance (Dynamic Binding/Run Time Polymorphism)

This Article summarizes the following points written by Akhil Mittal :

  • In C#, We can equate an object of a base class to a derived class but not vice versa.
  • The override modifier is needed as the derived class methods will get first priority and be called upon.
  • These modifiers like new and override can only be used if the method in the base class is a virtual method. Virtual means that the base class is granting us permission to invoke the method from the derived class and not the base class. But, we have to add the modifier override if our derived class method has to be called.
  • If the base class object declared the method virtual and the derived class used the modifier override, the derived class method will get called. Otherwise, the base class method will get executed. Therefore for virtual methods, the data type created is decided at run time only.
  • All the methods not marked with virtual are non virtual, and the method to be called is decided at compile time, depending upon the static data type of the object.
  • An override method is a method that has the override modifier included on it. This introduces a new implementation of a method. We can’t use the modifiers such as new, static or virtual along with override. But abstract is permitted.

Read full article – http://www.codeproject.com/Articles/774578/Diving-in-OOP-Day-Polymorphism-and-Inheritance-Dyn

Hope this will help !!!

Jay Ganesh

All About C# Access Modifiers

Access modifiers (or access specifiers) are keywords in object-oriented languages that set the accessibility of classes, methods, and other members. Access modifiers are a specific part of programming language syntax used to facilitate the encapsulation of components.

Summary of the article:

1) The default access modifier is private for class members.
2) A class marked as internal can have its access limited to the current assembly only.
3) Namespaces as we see by default can have no accessibility specifiers at all. They are by default public and we cannot add any other access modifier including public again too.
4) A class can only be public or internal. It cannot be marked as protected or private. The default is internal for the class.
5) Members of a class can be marked with all the access modifiers, and the default access modifier is private.
6) Protected internal means that the derived class and the class within the same source code file can have access.
7) Between public and internal, public always allows greater access to its members.
8) Base class always allows more accessibility than the derived class.
9) The return values of a method must have greater accessibility than that of the method itself.
10) A class marked sealed can’t act as a base class to any other class.
11) Since we cannot derive from sealed classes, the code from the sealed classes cannot be overridden.
12) We need to initialize the const variable at the time we create it. We are not allowed to initialize it later in our code or program.
13) Like classes, const variables cannot be circular, i.e., they cannot depend on each other.
14) A const field of a reference type other than string can only be initialized with null.
15) One can only initialize a const variable to a compile time value, i.e., a value available to the compiler while it is executing.
16) A constant by default is static and we can’t use the instance reference, i.e., a name to reference a const. A const has to be static as no one will be allowed to make any changes to a const variable.
17) A const variable cannot be marked as static.
18) A variable in C# can never have an uninitialized value.
19) Static variables are always initialized when the class is loaded first. An int is given a default value of zero and a bool is given a default of False.
20) An instance variable is always initialized at the time of creation of its instance.
21) A static readonly field cannot be assigned to (except in a static constructor or a variable initializer).

Rad full article

Jay Ganesh

Bind enum to ddl

Sometime we need to bind the value and the name of the enum to the dropdownlist. here is the code that will help us to achieve this.

here I have created a method to convert enum into hashtable :

    public Hashtable ConvertEnumToHashTable(Type myenum)
    {
        string[] names = Enum.GetNames(myenum);
        Array values = Enum.GetValues(myenum);
        Hashtable ht = new Hashtable();
        for (int i = 0; i < names.Length; i++)
        {
            ht.Add(Convert.ToInt32(values.GetValue(i)).ToString(), names[i]);
        }
        return ht;
    }

Now here is code that shows you how to use this function :

    protected void Page_Load(object sender, EventArgs e)
    {
        Hashtable ht = ConvertEnumToHashTable(typeof(myenum));
        myDDL.DataSource = ht;
        myDDL.DataTextField = "value";
        myDDL.DataValueField = "key";

        myDDL.DataBind();

    }

Hope this code will help !!!

Jay Ganesh

Base Page For Detecting Session Timeout in ASP.Net/C#

In this tutorial we will be going over how to create a base page class to handle your sessions. The number one question I get asked time and time again is how to manage sessions, and how to detect if a session has expired. Back in the days before .Net things were a little more complicated when it came to solving this riddle, but with the advent of the .Net Framework 2.0 a new class was introduced, the HttpSessionState Class, which is a member of the System.Web.SessionState Namespace. The new HttpSessionState Class gives us access to session state items and other lifetime management methods.

One of the items in the HttpSessionState class we will be looking at is the IsNewSession Property. This property lets us know whether the current session was created wtih the current request, or if it was an existing session. This is invaluable as we can use it to determine if the users session had expired or timed out. The IsNewSession Property is more robust and advanced then simply checking if the session is null because it takes into account a session timeout as well.

Read more