IQ

Static Constructor

Ø  Static constructor is first block of code to execute in class.

Ø  A static constructor is a constructor declared using a static modifier.

Ø  A static constructor is use to initialize static data

Ø  Static constructor does not take any parameters.

Ø  It is the first block of code executed in a class. With that, a static constructor executes only once in the life cycle of class.

class Demo

    {

        static int val1;

        int val2;

        static Demo()

        {

            Console.WriteLine("This is Static Constructor");

            val1 = 70;

        }

        public Demo(int val3)

        {

            Console.WriteLine("This is Instance Constructor");

            val2 = val3;

        }

        private void show()

        {

            Console.WriteLine("First Value = " + val1);

            Console.WriteLine("Second Value = " + val2);

        }

        static void Main(string[] args)

        {

            Demo d1 = new Demo(110);

            Demo d2 = new Demo(200);

            d1.show();

            d2.show();

            Console.ReadKey();

        }

    }

Ø  Private Constructor in C#?

Ø  Private constructor is constructor that is preceded by private access specifier. For example, below class has a private constructor.

Ø  We know that if we don’t write constructor in the class then by default constructor gets called on object creation which is public. Or if we want to allow object creation of the class then we write public constructor or else we explicitly specify private access specifier on class constructor.

Ø  Can we create object of class with private constructor in C#?Ø  No, object of a class having private constructor cannot be instantiated from outside of the class. However, we can create object of the class inside class methods itself.

class A {     //private constructor     private A()     {     } } class Program {     static void Main(string[] args)     {         A obj = new A();//Error cannot access private constructor     } }

 Ø  Use of private constructor in C# Sharp Programming:

Following are the scenarios when we can make use of private constructor in C# code.

 1)  Stop object creation of a class

If we want to stop object creation of a class, then we can make the class constructor private. So, if we try to create an object from the main program or other classes, then compiler will flash an error.

2) Use in Singleton class

We know that singleton class allows only single instance of it throughout the execution of the application. When we design a singleton class, we use private constructor, so, no user can create object of this class to stop multiple object creation. And singleton class itself provide the same object over and over on demand. 

3)  Stop a class to be inherited

Ø  If we don’t want a class to be inherited, then we make the class constructor private. So, if we try to derive another class from this class then compiler will flash an error. Why compiler will flash an error? We know the order of execution of constructor in inheritance that when we create an object of a derived class then first constructor of the base call will be called then constructor of derived class. Since, base class constructor is private, hence, derived class will fail to access base class constructor.

Ø  In below c sharp code example, compiler flashes error on creation of object of derived class or as soon as you write constructor of derived class.

//base class B {     private B()     {     } } //Derived class D : B {     public D()     {     }      } class Program {     static void Main(string[] args)     {        D obj = new D();//error     } }

Ø  Difference between Singleton Class and Static Class

Static Class:

1. You cannot create the instance of static class.
   
   
2. Loaded automatically by the .NET Framework common language runtime (CLR) when the program or namespace containing the class is loaded.
   
   
3. Static Class cannot have constructor.
   
   
4. We cannot pass the static class to method.
   
   
5. We cannot inherit Static class to another Static class in C#.

Singleton:

1. You can create one instance of the object and reuse it.
   
   
2. Singleton instance is created for the first time when the user requested. 
   
   
3. Singleton class can have constructor.
   
   
4. You can create the object of singleton class and pass it to method.
   
   
5. Singleton class does not say any restriction of Inheritance.
   
   
6. We can dispose the objects of a singleton class but not of static class.

WCF Predefined Bindings

1.   basicHttpBinding

basicHttpBinding is best when you have traditional ASMX(Active Server Methods) web services and needs to be replace with WCF. It supports text as well as MTOM encodings and it does not support WS-* standards like WS-Addressing, WS-Security and WS-ReliableMessaging.
basicHttpBinding uses HTTP or HTTPS protocols. You can configure SSL for Transport Layer security with basicHttpBinding.

2.   WsHttpBinding

This is secure and interoperable bindings uses SOAP over HTTP. With WsHttpBinding messages are encrypted by default and achieve message level security. It supports reliability, transactions and security over internet. It supports HTTP or HTTPS protocols and text as well as MTOM encoding.

The difference between basicHttpBinding and WsHttpBinding is WsHttpBinding does support WS-* standards like WS-Addressing, WS-Security and WS-ReliableMessaging

3.   wsDualHttpBinding

wsDualHttpBinding is best when you required bidirectional communication with client. In some scenario when client makes call to WCF service, after processing of long running request service has to call client application for example updating shipment details to client application.

It supports reliability, transactions and security over internet. It supports HTTP or HTTPS protocols and text as well as MTOM encoding. You can implement Duplex message exchange pattern with wsDualHttpBinding.

4.   webHttpBinding

webHttpBinding is best when you wish to implement RESTful WCF service. This is secure and interoperable binding which sends information directly over HTTP or HTTPS without creating SOAP messages. It allows HTTP request to use plain old XML (POX) style messaging which reduces the message size on wire compare to SOAP messages.

5.   NetTcpBinding

netTcpBinding is best when WCF service and its clients are in intranet infrastructure. As it supports only TCP protocol and not HTTP so service cannot be accessed over internet.

This is secure binding is used to send binary encoded SOAP messages with in intranet computers. It supports reliability, transaction and security. If your using netTcpBinding and host WCF service in IIS, you need to make some settings on system and IIS this article will help you for required settings.

6.   netNamedPipeBinding

When your WCF service and its clients reside on same computer netNamedPipeBinding is the best choice and gives best performance over other bindings. This is secure bindings. Binary encoded SOAP messages are sent over named pipes.

See how to implement netNamedPipeBinding in WCF services.

7.   netPeerTcpBinding

netPeerTcpBinding is best when you require more security for peer to peer communication as netTcpBinding does not provide it. It is secure binding and supports TCP protocols.

8.   WsFederationHttpBinding

It is secure and interoperable binding supports federated security. It supports HTTP and HTTPS transport protocols as well as text and MTOM encodings.

9.   NetMsmqBinding

netMsmqBinding is best when you have to execute service operations in queued manner. Service requests are placed in queue and executed one by one. With netMsmqBinding service operations will always be one way and does not return any response to client.

• How implement security in WCF