Friday, October 29, 2010

Difference between Web Service and WCF Service

While taking interviews of .NET developers I often ask this questions. But lots of people don’t know exact difference between this. So, I decided to write a separate blog about this.

Here are the few differences.

  • Web services can be hosted in IIS as well as outside of the IIS. While WCF service can be hosted in IIS, Windows activation service,Self Hosting,WAS and on lots of proctols like Named Pipe,TCP etc.Here lots of people disagree how we can host the web service outside of the IIS but Here is the article for that.http://msdn.microsoft.com/en-us/library/aa529311.aspx.
  • In Web Services Web Service attribute will added  on the top of class. In WCF there will be a Service Contract attributes will be there. Same way Web Method attribute are added in top of method of Web service while in WCF Service Operation Contract will added on the top method.
  • In Web service System.XML.Serialization is supported while in the WCF Service System.RunTime.Serialization is supported.
  • WCF Services can be multithreaded via ServiceBehavior class while web service can not be.
  • WCF Services supports different type of bindings like BasicHttpBinding, WSHttpBinding, WSDualHttpBinding etc.while Web services only used soap or xml for this.
  • Web services are compiled into a class library assembly. A file called the service file is provided that has the extension .asmx and contains an @ WebService directive that identifies the class that contains the code for the service and the assembly in which it is located while in WCF.WCF services can readily be hosted within IIS 5.1 or 6.0, the Windows Process Activation Service (WAS) that is provided as part of IIS 7.0, and within any .NET application. To host a service in IIS 5.1 or 6.0, the service must use HTTP as the communications transport protocol.

Hope this will help you. Happy programming!!!

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Tuesday, October 26, 2010

Output Caching in asp.net

Recently one of my friend ask about output cache so I decided to put a post about how output cache works and what is the advantages and disadvantage of using output cache. Output cache is a technique to cache generated response from the asp.net pages or controls. Output Caching increases the performance drastically by reducing server round trips. We can use @OutputCache directive to controls output caching for a page or controls.

The @OutputCache includes following attributes.

  • Duration: This attribute will explain how long output cache will be there for a page or control. It can be set in seconds. If you set 60 then it will not going to generate response from server until 60 second It will generate response from the cache it self. Here is example of duration where it will set 60 second for page.
  • <%@ OutputCache Duration="60" %>  

  • VaryByParam: This attribute will determine cache entries based on get or post parameters. It will vary cache based on get or post parameters suppose you set product Id query string as VaryByParam it will create a different cache based on product Id. Following is a example how you can set the VaryByParam based on Product Id.
  • <%@ OutputCache Duration="Seconds" VaryByParam="ProductId"%>
    

  • Location: This attribute will specify where the Item will be cached. Here are options available for that.
    • Any: The output cache can be located at any browser from where request is generated or Server where request is processed or Proxy server participating in request.
    • Client: The output cache will be located on browser client from where request is generated.
    • Downstream: The output cache can be stored in any HTTP 1.1 cache-capable devices other than the origin server. This includes proxy servers and the client that made the request.
    • Server: The output cache will stored in the server where generated request will be processed.
    • ServerAndClient: The output cache will generated either on Browser where request generated or on server where generated request will be processed. Proxy servers are not allowed for this.
    • None: None specifies that output cache will be disabled for this controls or Page.
Here is example of location.

      <%@ outputcache duration="10"  Location="Server" %>
      

  • VaryByCustom: This attribute is for different browsers where request is generated this means it will generate new instance of cache based on different browser versions.
  • <%@ OutputCache Duration="Seconds" VaryByCustom="Browser" %>
  • VaryByHeader: This attribute allows to determine different instances of cache based on the headers. Here is example for it.
  • <%@ OutputCache VaryByHeader="Accept-Language" %>
    
Note: If you specify the output cache it will not fire server side events like click or selected index changed etc. So make sure the controls that you used in output cache will not have this kind of controls Or you have to handle this in other scenarios.

Hope this will help you.. Happy programming!!

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Difference between sliding expiration and absolute expiration

ASP.net cache is great feature through which we can increase the performance of the our web application via reducing server round trips to database. We can cache any serializable data into the cache. There are so many ways to cache data but one of the simplest way to cache data like insert data into cache object. Here we must need to validate cache if any data is changed and there are so many ways from where we can set dependency to validate the cache like files,SQL Cache Dependency etc. We also can validate cache or expire via setting time to duration to its object. Like after the defined time our cache will expire and then it will again put new fresh data into the cache. This is called as time base expiration. We can put this kind of expiration via two way.

  1. Absolute Expiration
  2. Sliding Expiration

Absolute Expiration: Absolute expiration means It will expire cache after some time period set at the time of activating cache. This will be absolute expiration whether cache will be used or not It will expire the cache. This type of expiration used to cache data which are not frequently changing.

Sliding Expiration: Sliding expiration means It will expire cache after time period at the time of activating cache if any request is not made during this time period. This type of expiration is useful when there are so many data to cache. So It will put those items in the cache which are frequently used in the application. So it will not going to use unnecessary memory.

Here is the example how we can set the sliding expiration and absolute expiration.

string cacheData = "The data to be cached";
//Absolute Expiration
Cache.Insert("AbsoluteCacheKey", cacheData, null,
DateTime.Now.AddMinutes(1), System.Web.Caching.Cache.NoSlidingExpiration);
//Sliding Expiration
Cache.Insert("SlidingExpiration", cacheData, null,
System.Web.Caching.Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(1));
In above example I have created the a string to be cache that can be any serialized data. In the absolute expiration you can see that it will expires after one minute whether its accessed or not. While in sliding expiration it will expire cache if cache is not accessed within specified time.

Hope this will help you for better understanding of asp.net caching technique. Happy programming!!!

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