WCF Throttling

WCF throttling provides some properties that you can use to limit how many instances or sessions are created at the application level. Performance of the WCF service can be improved by creating proper instance.

Attribute	Description
maxConcurrentCalls	Limits the total number of calls that can currently be in progress across all service instances. The default is 16.
maxConcurrentInstances	The number of InstanceContext objects that execute at one time across a ServiceHost. The default is Int32.MaxValue.
maxConcurrentSessions	A positive integer that limits the number of sessions a ServiceHost object can accept. The default is 10.

Service Throttling can be configured either Adminstractive or Programatically

Administrative(configuration file)

Using <serviceThrottling> tag of the Service Behavior, you can configure the maxConcurrentCalls, maxConcurrentInstances , maxConcurrentSessions property as shown below.

<system.serviceModel>
    <services >
      <service behaviorConfiguration="ServiceBehavior"  name="MyService">
        <endpoint address="" binding="wsHttpBinding" contract="IMyService">
          <identity>
            <dns value="localhost"/>
          </identity>
        </endpoint>
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="ServiceBehavior">
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="true "/>
          <serviceThrottling maxConcurrentCalls="500"
 maxConcurrentInstances ="100" 
maxConcurrentSessions ="200"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>

Programming Model

Use ServiceThrottlingBehavior object to set concurrent calls, session and instance property.

ServiceHost host = new ServiceHost(typeof(MyService));
           ServiceThrottlingBehavior throttle
 = host.Description.Behaviors.Find();
            if (throttle == null)
            {
                throttle = new ServiceThrottlingBehavior();
                throttle.MaxConcurrentCalls = 500;
                throttle.MaxConcurrentSessions = 200;
                throttle.MaxConcurrentInstances = 100;
                host.Description.Behaviors.Add(throttle);
            }

            host.Open();
   

Metadata Exchange Endpoint

Exposing the metadata using HTTP-GET has a disadvantage, such that there is no guarantee that other platforms you interact will support it. There is other way of exposing the using special endpoint is called as Metadata Exchange Endpoint. You can have as many metadata exchange endpoints as you want.

Address

It is basically Uri to identify the metadata. You can specify as address in the endpoint but append with "mex" keyword. For example "http://localhost:9090/MyCalulatorService/mex"

Binding

There are four types of bindings supported for metadata exchange. They are mexHttpBinding, mexHttpsBinding, mexNamedPipesBinding, mexTcpBinding.

Contract

IMetadataExchange is the contract used for MEX endpoint. WCF service host automatically provides the implementation for this IMetadataExcahnge while hosting the service.

You can create the Metadata Exchange Endpoint either Administrative (configuration file) or programmatically.

Administrative (Configuration file):

In the configuration file of the hosting application, you can add metadata exchange endpoint as shown below.

<system.serviceModel>
<services>
 <service name="MyService">
 <endpoint address="http://localhost/IISHostedService/MyService.svc"
 binding="wsHttpBinding" contract="IMyService">
 <identity>
 <dns value="localhost"/>
 </identity>
 </endpoint>
 <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
 </service>
</services>  
</system.serviceModel>

Programming Model:

In the following code I have mention about creating the Metadata Exchange Endpoint through coding. Steps to create the metadata endpoint are

• Create the ServiceMetadataBehavior object and add to Service host description.

ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            host.Description.Behaviors.Add(smb);

• Create the metadata binding object using MetadataExchangeBinding

Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();

• 3. Add the endpoint to the service host with address, binding and contract.

host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");

Complete code for hosting the service with metadata exchange endpoint is shown below.

//Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            ServiceHost host = new 
            ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);
            //Add a service endpoint
            host.AddServiceEndpoint
            (typeof(MyCalculatorService.ISimpleCalculator), new WSHttpBinding(), "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            host.Description.Behaviors.Add(smb);
            Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();
            //Adding metadata exchange endpoint
            host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");
            //Start the Service
            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());
            Console.WriteLine("Host is running... Press  key to stop");
            Console.ReadLine();

WCF Architecture

The following figure illustrates the major components of WCF.

Contracts

Contracts layer are next to that of Application layer. Developer will directly use this contract to develop the service. We are also going to do the same now. Let us see briefly what these contracts will do for us and we will also know that WCF is working on message system.

Service contracts

- Describe about the operation that service can provide. Example, Service provided to know the temperature of the city based on the zip code, this service we call as Service contract. It will be created using Service and Operational Contract attribute.

Data contract

- It describes the custom data type which is exposed to the client. This defines the data types, are passed to and from service. Data types like int, string are identified by the client because it is already mention in XML schema definition language document, but custom created class or datatype cannot be identified by the client e.g. Employee data type. By using DataContract we can make client aware that we are using Employee data type for returning or passing parameter to the method.

Message Contract

- Default SOAP message format is provided by the WCF runtime for communication between Client and service. If it is not meeting your requirements then we can create our own message format. This can be achieved by using Message Contract attribute.

Policies and Binding

- Specify conditions required to communicate with a service e.g security requirement to communicate with service, protocol and encoding used for binding.

Service Runtime

- It contains the behaviors that occur during runtime of service.

• Throttling Behavior- Controls how many messages are processed.
• Error Behavior - Specifies what occurs, when internal error occurs on the service.
• Metadata Behavior - Tells how and whether metadata is available to outside world.
• Instance Behavior - Specifies how many instance of the service has to be created while running.
• Transaction Behavior - Enables the rollback of transacted operations if a failure occurs.
• Dispatch Behavior - Controls how a message is processed by the WCF Infrastructure.

Messaging

- Messaging layer is composed of channels. A channel is a component that processes a message in some way, for example, by authenticating a message. A set of channels is also known as a channel stack. Channels are the core abstraction for sending message to and receiving message from an Endpoint. Broadly we can categories channels as

• Transport Channels Handles sending and receiving message from network. Protocols like HTTP, TCP, name pipes and MSMQ.
• Protocol Channels Implements SOAP based protocol by processing and possibly modifying message. E.g. WS-Security and WS-Reliability.

Activation and Hosting

- Services can be hosted or executed, so that it will be available to everyone accessing from the client. WCF service can be hosted by following mechanism

• IIS Internet information Service provides number of advantages if a Service uses Http as protocol. It does not require Host code to activate the service, it automatically activates service code.
  
• Windows Activation Service (WAS) is the new process activation mechanism that ships with IIS 7.0. In addition to HTTP based communication, WCF can also use WAS to provide message-based activation over other protocols, such as TCP and named pipes.
  
• Self-Hosting WCF service can be self hosted as console application, Win Forms or WPF application with graphical UI.
  
• Windows Service WCF can also be hosted as a Windows Service, so that it is under control of the Service Control Manager (SCM).

WCF Hosting

We are going to see the four different way of hosting the WCF service. WCF service cannot exist on its own; it has to be hosted in windows process called as host process. Single host process can host multiple servers and same service type can be hosted in multiple host process. As we discussed there are mainly four different way of hosting the WCF service.

1. IIS hosting
2. Self hosting
3. Windows Activation Service
4. Windows Service

Multiple hosting and protocols supported by WCF.Microsoft has introduced the WCF concept in order to make distributed application development and deployment simple.

Hosting Environment	Supported protocol
Windows console and form application	HTTP,net.tcp,net.pipe,net.msmq
Windows service application (formerly known as NT services)	HTTP,net.tcp,net.pipe,net.msmq
Web server IIS6	http, wshttp
Web server IIS7 - Windows Process Activation Service (WAS)	HTTP,net.tcp,net.pipe,net.msmq

A summary of hosting options and supported features.

Feature	Self-Hosting	IIS Hosting	WAS Hosting
Executable Process/ App Domain	Yes	Yes	Yes
Configuration	App.config	Web.config	Web.config
Activation	Manual at startup	Message-based	Message-based
Idle-Time Management	No	Yes	Yes
Health Monitoring	No	Yes	Yes
Process Recycling	No	Yes	Yes
Management Tools	No	Yes	Yes

Types of Binding in WCF

BasicHttpBinding

• It is suitable for communicating with ASP.NET Web services (ASMX)-based services that comfort with WS-Basic Profile conformant Web services.
• This binding uses HTTP as the transport and text/XML as the default message encoding.
• Security is disabled by default
• This binding does not support WS-* functionalities like WS- Addressing, WS-Security, WS-ReliableMessaging
• It is fairly weak on interoperability.

WSHttpBinding

• Defines a secure, reliable, interoperable binding suitable for non-duplex service contracts.
• It offers lot more functionality in the area of interoperability.
• It supports WS-* functionality and distributed transactions with reliable and secure sessions using SOAP security.
• It uses HTTP and HTTPS transport for communication.
• Reliable sessions are disabled by default.

WSDualHttpBinding

This binding is same as that of WSHttpBinding, except it supports duplex service. Duplex service is a service which uses duplex message pattern, which allows service to communicate with client via callback.
In WSDualHttpBinding reliable sessions are enabled by default. It also supports communication via SOAP intermediaries.

WSFederationHttpBinding

This binding support federated security. It helps implementing federation which is the ability to flow and share identities across multiple enterprises or trust domains for authentication and authorization. It supports WS-Federation protocol.

NetTcpBinding

This binding provides secure and reliable binding environment for .Net to .Net cross machine communication. By default it creates communication stack using WS-ReliableMessaging protocol for reliability, TCP for message delivery and windows security for message and authentication at run time. It uses TCP protocol and provides support for security, transaction and reliability.

NetNamedPipeBinding

This binding provides secure and reliable binding environment for on-machine cross process communication. It uses NamedPipe protocol and provides full support for SOAP security, transaction and reliability. By default it creates communication stack with WS-ReliableMessaging for reliability, transport security for transfer security, named pipes for message delivery and binary encoding.

NetMsmqBinding

• This binding provides secure and reliable queued communication for cross-machine environment.
• Queuing is provided by using MSMQ as transport.
• It enables for disconnected operations, failure isolation and load leveling

NetPeerTcpBinding

• This binding provides secure binding for peer-to-peer environment and network applications.
• It uses TCP protocol for communication
• It provides full support for SOAP security, transaction and reliability.

Why ADO.NET is better from ADO?

The ADO.NET is better from ADO by the below reasons-

Describe about the various types of generic collections?

There are basically four different types of generic collections which are as follows:-

1. List:-Lists are indexed based Generic Collections. Lists are Generic form of ArrayList.

List helps us to create flexible strong type collection as you can see in below code snippet i have defined List as "int" and "string".

////index based Generic collection           
List<int> ObjInt = new List<int>();        
ObjInt.Add(123);           
ObjInt.Add(456);           
Console.WriteLine(ObjInt[0]); //accessing the List by internal index based value.           
List<string> ObjString = new List<string>();           
ObjString.Add("feroz");

2. Dictionary:-Dictionary are key based generics collection.

Dictionary are generic form of Hashtable.

////key based Generic collection           
Dictionary<int, int> ObjDict = new Dictionary<int,int>();           
ObjDict.Add(1,2);           
Dictionary<int, string> ObjDict1 = new Dictionary<int,string>();           
ObjDict1.Add(3, "feroz is a developer");           
ObjDict1.Add(4, "wasim is a developer");           
Console.WriteLine(ObjDict1[3]); //accessing the dictionary by defined key.

3. Stack:-Stack generic collection allows you to get value in "LIFO"(last in first out) manner.

//// Stack            
Stack<string> ObjStack = new Stack<string>();           
ObjStack.Push("feroz");           
ObjStack.Push("moosa");           
Console.WriteLine(ObjStack.Pop());

4. Queue:-Queue generic collection allows you to get value in "FIFO"(first in first out) manner.

////Queue           
Queue<int> ObjStr = new Queue<int>();           
ObjStr.Enqueue(789);           
ObjStr.Enqueue(456);           
Console.WriteLine(ObjStr.Dequeue());

What are endpoints, address, contracts and bindings?

Elaborate different types of assemblies?

In .NET there are basically three different types of assemblies as follows.

1.Private assemblies:-A private assembly is normally used by a single application and is stored in the application's directory.

2.Public/shared assemblies:- A shared assembly is normally stored in the global assembly cache which is a repository of assemblies maintained by the .NET runtime.
3.satellite assemblies:-Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language.

How to consume WebService in Ajax?

How to create the service using WCF - Part 1

In a parent child relationship which constructor fires first ?

c# and .NET Interview questions :- What are Generics

Master Page Life Cycle

Master Page sequence of events / Life Cycle

1) Master Controls Init
2) Content Controls Init

3) Master Page Init
4) Content Page Init

5) Content Page Load
6) Master Page Load

7) Master Controls Load
8) Content Controls Load

9) Content Page PreRender
10) Master Page PreRender

11) Master Control PreRender
12) Content Control PreRender

13) Master Controls Unload
14) Content Controls Unload

15) Master Page Unload
16) Content Page Unload

--Kishore

For more detailed explanation about Master & Content page event. Go through the below link

http://odetocode.com/articles/450.aspx
http://englestone.blogspot.com/2008/06/master-page-sequence-of-events.html

difference between window.onload and document.ready

Document.ready() function is different from body onload() function because off 2 reasons.

1. We can have more than one document.ready() function in a page where we can have only one onload function.
2. Document.ready() function is called as soon as DOM is loaded where body.onload() function is called when everything gets loaded on the page that includes DOM, images and all associated resources of the page. 

Interfaces in C#

Here is the link for implementation of interfaces with examples:  


http://www.codeproject.com/KB/cs/cs_interfaces.aspx