What is Backward compatibility in .Net

   What is Backward compatibility

 

Backward compatibility means that an app that was developed for a particular version of a platform will run on later versions of that platform. The .NET Framework tries to maximize backward compatibility: Source code written for one version of the .NET Framework should compile on later versions of the .NET Framework, and binaries that run on one version of the .NET Framework should behave identically on later versions of the .NET Framework

 

The .NET Framework 4.5 and its point releases are backward-compatible with apps that were built with earlier versions of the .NET Framework. In other words, apps and components built with previous versions will work without modification on the .NET Framework 4.5. However, by default, apps run on the version of the common language runtime for which they were developed, so you may have to provide a configuration file to enable your app to run on the .NET Framework 4.5. For more information

      

ü  Note that the .NET Framework 4.5 is not supported on Windows XP.

ü  .net 4.5 comes automatically with windows 8

ü  .net 3.5 sp1 comes automatically with windows 7 sp1

http://bytes.com/topic/asp-net/insights/952841-what-backward-compatibility-net

Relationship between CLR and .Net framework version

It  depends upon CLR for .net framework we are using.
a) NET Framework 2.0, 3.0, and 3.5 include CLR 2.0.
b) .NET Framework 4, 4.5, and 4.5.1 include CLR 4.0
c) CLR 3.0 does not exist
d) Application developed in 2.0,3.0 can run in 3.5 framework because target CLR is same
but application developed in 3.0 will not run on 4.5 framework because now target framework is different (CLR4)


NET Framework 1.0: "v1.0.3705"
o .NET Framework 1.1: "v1.1.4322"
o .NET Framework 2.0, 3.0, and 3.5: "v2.0.50727"
o .NET Framework 4 and 4.5 (including point releases such as 4.5.1): "v4.0


http://bytes.com/topic/asp-net/insights/952842-relation-ship-between-clr-net-framework-version

Array support more than two gigabyte size in .Net 4.5

Problem Statement

Sometimes with 64-bit support on the .NET Framework is the limitation on arrays, which cannot exceed 2 GB. One of the main reasons you move to 64-bit platforms is to access more than 2 GB, and this limitation was a big problem for those of us trying to work with large matrices and vectors. No matter the amount of available RAM available, it was very common to have a System.OutOfMemoryException

Solution

.NET Framework 4.5 introduces a configuration attribute in the run-time schema that enables arrays larger than 2 GB in total size on 64-bit applications. You need only enable the gcAllowVeryLargeObjects element that controls the behavior of the .NET garbage-collection system.

<configuration>
< startup>
< supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
< /startup>
< runtime>
< gcAllowVeryLargeObjects enabled="true" />
< /runtime>
< /configuration>

http://bytes.com/topic/net/insights/952845-array-support-more-than-two-gigabyte-size-net-4-5-a#post3760563

 

Session_End event does not fire in OutProc session mode

Session_End is Fired when a user's session times out.
When Webserver did not get any response for 20 min by default then Session_end automatically fires.

Another important thing to write this topic here is that, Session_end only fires incase of Inproc session mode, not for Outproc session mode.

We can use Session.Abandon to force this.


Remember the Session_End event will not fire in case the user closes the browser. HTTP is a stateless protocol. There is no way for the server to understand that the browser has been closed.

Happy Coding !!!!!!!!!!!!!!!

Session_end for InProc and OutProc session mode in Asp.net

Session_End is Fired when a user's session times out.
When Webserver did not get any response for 20 min by default then Session_end automatically fires.

We can use Session.Abandon to force this.

Another important thing to write this topic here is that, Session_end only fires incase of Inproc session mode, not for Outproc session mode.

Remember the Session_End event will not fire in case the user closes the browser. HTTP is a stateless protocol. There is no way for the server to understand that the browser has been closed.

Happy Coding !!!!!!!!!!!!!!!

Garbage Collection Improvement in .Net 4.5

Problem statement

Garbage collector is one real heavy task in a .NET application. And it becomes heavier when it is an ASP.NET application. ASP.NET applications run on the server and a lot of clients send requests to the server thus creating loads of objects, making the GC really work hard for cleaning up unwanted objects.

Solution

Concurrent garbage collection

To overcome the above problem, server GC was introduced. In server GC there is one more thread created which runs in the background. This thread works in the background and keeps cleaning. objects thus minimizing the load on the main GC thread. Due to double GC threads running, the main application threads are less suspended, thus increasing application throughput. To enable server GC,  following to do

<configuration>

                      <runtime>
                            <gcServer enabled="true"/>
                                      </runtime>
                           </configuration>

Profile optimization (Improved startup performance) in .Net 4.5

This is also known as Multicore JIT

Problem
When the application is run, the IL code is read by the CLR and JIT compiled into native code for the particular machine

So the compilation from the IL Code to the native code happens when the application is actually running. So application generally takes lot of time at start up.

 

Profile optimization is improvement over start up time.

 

Profile optimization

 

·         The fundamental problem with JIT compilation is , Jitting is normally a lazy operation, it Jits a method and do not know what next method is for jitting. So the solution is it has to remember something from previous run which is all the jitting that happened

 

·         .net framework 4.5 supports this optimization using application profiles. Now we can enable the profile optimization for an application. Based on the historic profile, it keeps JIT compiling the methods in the background. So when the code is actually needed for execution, it is already in native format so the runtime doesn't have to wait for this.

 

·         Profile is nothing but a simple file which has a list of methods which the application will need during startup

 

·         Multicore JIT parallelizes the some of the JIT compilations that happens on the start of the application

 

Profile optimization requires a multicore computer. The methods are ignored on other computers

Async and await in .Net 4.5

Before moving ahead I want to introduce basic concept of Asynchronous Programming

 

Problem

Sometimes   in our web application we request for data from webserver and we have to wait for response. So in this case our entire application is blocked and user have to wait till response from webserver.

 

Solution

Asynchronous Programming is introduced to overcome above problem.

 

Async Improves Responsiveness

Asynchrony is essential for activities that are potentially blocking, such as when your application accesses the web. Access to a web resource sometimes is slow or delayed. If such an activity is blocked within a synchronous process, the entire application must wait. In an asynchronous process, the application can continue with other work that doesn't depend on the web resource until the potentially blocking task finishes

Difference between synchronous/asynchronous operations

a)      Synchronization means two or more operations are running in a same context (thread) so that one may block another

b)      Synchronization means two or more operations happen sequentially.

c)       Asynchronous means two or more operations are running in different contexts (thread) so that they can run concurrently and do not block each other.

  

Synchronous operation (fig 1)	Asynchronous operation (fig 2)

 

 Explanation

1)      From fig 1

a.       Each task occurs in sequence.

b.      Here from fig, step3 have to wait to complete step2

 

2)      From fig2

a.        async and await keywords has been introduced

b.      async and await are pair keywords. You cannot use them in a standalone manner.

c.       async is marked on a method. This keyword is just an indicator saying that this method will have the await keyword.

d.      The await keyword marks the position from where the task should resume. So you will always find this keyword in conjunction with Task.

        Here Step3 will execute without waiting for step2 to complete