Introduction of  Dot net 4.0 to 4.5

.NET Framework 4

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NET Framework 4 on 29 September 2008. The Public Beta was released on 20 May 2009.

• Parallel Extensions to improve support for parallel computing, which target multi-core or distributed systems. To this end, technologies like PLINQ (Parallel LINQ), a parallel implementation of the LINQ engine, and Task Parallel Library, which exposes parallel constructs via method calls., are included.
• New Visual Basic .NET and C# language features, such as implicit line continuations, dynamic dispatch, named parameters, and optional parameters.
• Support for Code Contracts.
• Inclusion of new types to work with arbitrary-precision arithmetic (System.Numerics.BigInteger) and complex numbers (System.Numerics.Complex).
• Introduce Common Language Runtime (CLR) 4.0.
• Parallel Thread Processing(Task).

Core Features

• Ability to limit how long the regular expression engine will attempt to resolve a regular expression before it times out.
• Ability to define the culture for an application domain.
• Console support for Unicode (UTF-16) encoding.
• Support for versioning of cultural string ordering and comparison data.
• Better performance when retrieving resources.
• Zip compression improvements to reduce the size of a compressed file.
• Ability to customize a reflection context to override default reflection behavior through the CustomReflectionContext class.

Managed Extensibility Framework (MEF)

• Support for generic types.
• Convention-based programming model that enables you to create parts based on naming conventions rather than attributes.
• Multiple scopes.

Tools

• Resource File Generator (Resgen.exe) enables you to create a .resw file for use in Windows Store apps from a .resources file embedded in a .NET Framework assembly.
• Managed Profile Guided Optimization (Mpgo.exe) enables you to improve application startup time, memory utilization (working set size), and throughput by optimizing native image assemblies. The command-line tool generates profile data for native image application assemblies.

.NET Framework 4.5

• NET for Metro style Apps
• Portable Class Libraries
• Core New Features and Improvements
• Parallel Computing
• Web
• Networking
• Windows Presentation Foundation (WPF)
• Windows Communication Foundation (WCF)
• Windows Workflow Foundation (WF)
• The features of .NET framework 4.5
  To summarize:
  

  • Installation
    .NET Framework 4.5 does not support Windows XP or Windows Server 2003, and therefore, if you have to create applications that target these operating systems, you will need to stay with .NET Framework 4.0. In contrast, Windows 8 and Windows Server 2012 in all of their editions include .NET Framework 4.5.
  • Support for Arrays Larger than 2 GB on 64-bit Platforms
  • Enhanced Background Server Garbage Collection
  • Support for Timeouts in Regular Expression Evaluations
  • Support for Unicode 6.0.0 in Culture-Sensitive Sorting and Casing Rules on Windows 8
  • Simple Default Culture Definition for an Application Domain
  • Internationalized Domain Names in Windows 8 Apps

 

Core new features and improvements

• Ability to reduce system restarts by detecting and closing .NET Framework 4 applications during deployment. See Reducing System Restarts During .NET Framework 4.5 Installations.
  
• Support for arrays that are larger than 2 gigabytes (GB) on 64-bit platforms. This feature can be enabled in the application configuration file. See the <gcAllowVeryLargeObjects> element, which also lists other restrictions on object size and array size.
  
• Better performance through background garbage collection for servers. When you use server garbage collection in the .NET Framework 4.5, background garbage collection is automatically enabled. See the Background Server Garbage Collection section of the Fundamentals of Garbage Collection topic.
  
• Background just-in-time (JIT) compilation, which is optionally available on multi-core processors to improve application performance. See ProfileOptimization.
  
• Ability to limit how long the regular expression engine will attempt to resolve a regular expression before it times out. See the Regex.MatchTimeout property.
  
• Ability to define the default culture for an application domain. See the CultureInfo class.
  
• Console support for Unicode (UTF-16) encoding. See the Console class.
  
• Support for versioning of cultural string ordering and comparison data. See the SortVersion class.
  
• Better performance when retrieving resources. See Packaging and Deploying Resources in Desktop Apps.
  
• Zip compression improvements to reduce the size of a compressed file. See the System.IO.Compression namespace.
  
• Ability to customize a reflection context to override default reflection behavior through the CustomReflectionContext class.
  
• Support for the 2008 version of the Internationalized Domain Names in Applications (IDNA) standard when the System.Globalization.IdnMapping class is used on Windows 8.
  
• Delegation of string comparison to the operating system, which implements Unicode 6.0, when the .NET Framework is used on Windows 8. When running on other platforms, the .NET Framework includes its own string comparison data, which implements Unicode 5.x. See the String class and the Remarks section of the SortVersion class.
  
• Ability to compute the hash codes for strings on a per application domain basis. See <UseRandomizedStringHashAlgorithm> Element.
  
• Type reflection support split between Type and TypeInfo classes. See Reflection in the .NET Framework for Windows Store Apps.
  
  

  Parallel computing
  

  The .NET Framework 4.5 provides several new features and improvements for parallel computing. These include improved performance, increased control, improved support for asynchronous programming, a new dataflow library, and improved support for parallel debugging and performance analysis.
  
  

Enhanced Background Server Garbage Collection

.NET Framework 4.5 changes the default mode for server garbage collection to the new background server garbage collection. Thus, whenever you enable the gcServer element in the run-time schema to change from the default workstation garbage collection to server garbage collection, you will be activating the new mode.
For example, line 7 in the following App.config example of a 64-bit .NET Framework 4.5 console application activates background server garbage collection:

Example :

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<?xml version="1.0" encoding="utf-8" ?> <configuration>     <startup>         <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />     </startup>     <runtime>       <gcServer enabled ="true" />     </runtime> </configuration>

A common problem with previous versions of the .NET Framework with multithreaded applications was frequent garbage collections that blocked all the threads until the collection completed. That was typical with workstation garbage collection and the pattern is known as "workstation garbage collection overhead."
Whenever you couldn't reduce the memory pressure in your algorithms, you usually achieved a speedup by enabling the server garbage collection, also known as "Server GC," by simply enabling the gcServer element in the run-time schema. The Server GC would maximize throughput and improve scalability as the number of available cores increased because it dedicated more threads to garbage collection and reduced the overall time to complete garbage collection. The drawback was that it required scheduling more threads than the workstation garbage collection mechanism.
The new background server garbage collection usually creates a managed heap and one dedicated background garbage-collection thread per logical core. Each background garbage-collection thread has its appropriate thread-affinity setting assigned to each available logical core. These background garbage-collection threads don't time out and can remove dead objects and expand heap. The improved algorithms reduce the amount of foreground garbage collections, and hence, improve overall throughput.
The good news is that you don't have to make changes in your code. If you were already using server garbage collection, you will usually notice increased throughput and fewer threads blocked until foreground collection finishes in .NET Framework 4.5.

Support for Timeouts in Regular Expression Evaluations

.NET Framework 4.5 introduces a new constructor for the System.Text.RegularExpressions.Regex class that accepts a TimeSpan matchTimeout parameter to establish a timeout for the regular expression resolution. When you specify a value for the new matchTimeout parameter, if the regular expression engine doesn't resolve the regular expression in the specified time, it will throw a RegexMatchTimeoutException exception. This way, when you have very complex regular expressions, you have an easy way to establish a timeout and you don't have to use complex workarounds to generate your own timeout mechanisms.
The following code uses the new constructor with a 1000 milliseconds TimeSpan parameter to establish a 1,000 milliseconds timeout:

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var regex = new Regex(     @"^(?<proto>\w+)://[^/]+?(?<port>:\d+)?/",     RegexOptions.None,     TimeSpan.FromMilliseconds(1000));

 Asynchronous operations

In the .NET Framework 4.5, new asynchronous features were added to the C# and Visual Basic languages. These features add a task-based model for performing asynchronous operations.

Windows Communication Foundation (WCF)

In the .NET Framework 4.5, the following features have been added to make it simpler to write and maintain Windows Communication Foundation (WCF) applications:

• Simplification of generated configuration files.
• Support for contract-first development.
• Ability to configure ASP.NET compatibility mode more easily.
• Changes in default transport property values to reduce the likelihood that you will have to set them.
• Updates to the XmlDictionaryReaderQuotas class to reduce the likelihood that you will have to manually configure quotas for XML dictionary readers.
• Validation of WCF configuration files by Visual Studio as part of the build process, so you can detect configuration errors before you run your application.
• New asynchronous streaming support.
• New HTTPS protocol mapping to make it easier to expose an endpoint over HTTPS with Internet Information Services (IIS).
• Ability to generate metadata in a single WSDL document by appending ?singleWSDL to the service URL.
• Websockets support to enable true bidirectional communication over ports 80 and 443 with performance characteristics similar to the TCP transport.
• Support for configuring services in code.
• XML Editor tooltips.
• ChannelFactory caching support.
• Binary encoder compression support.
• Support for a UDP transport that enables developers to write services that use "fire and forget" messaging. A client sends a message to a service and expects no response from the service.
• Ability to support multiple authentication modes on a single WCF endpoint when using the HTTP transport and transport security.
• Support for WCF services that use internationalized domain names (IDNs).

What's new in the .NET Framework 4.5.1

• You can use Windows Runtime APIs in portable libraries that target Windows 8.1, Windows Phone 8.1, and Windows Phone Silverlight 8.1.
  
• You can include XAML (Windows.UI.XAML types) in portable libraries when you target Windows 8.1 or Windows Phone 8.1. The following XAML templates are supported: Blank Page, Resource Dictionary, Templated Control, and User Control.
  
• You can create a portable Windows Runtime component (.winmd file) for use in Store apps that target Windows 8.1 and Windows Phone 8.1.
  
• You can retarget a Windows Store or Windows Phone Store class library like a Portable Class Library.
  
  Improvements when debugging your .NET Framework apps in Visual Studio 2013 include:
  
• Return values in the Visual Studio debugger. When you debug a managed app in Visual Studio 2013, the Autos window displays return types and values for methods. This information is available for desktop, Windows Store, and Windows Phone apps. For more information, see Examine return values of method calls in the MSDN Library.
  
• Edit and Continue for 64-bit apps. Visual Studio 2013 supports the Edit and Continue feature for 64-bit managed apps for desktop, Windows Store, and Windows Phone. The existing limitations remain in effect for both 32-bit and 64-bit apps
  
• Async-aware debugging. To make it easier to debug asynchronous apps in Visual Studio 2013, the call stack hides the infrastructure code provided by compilers to support asynchronous programming, and also chains in logical parent frames so you can follow logical program execution more clearly. A Tasks window replaces the Parallel Tasks window and displays tasks that relate to a particular breakpoint, and also displays any other tasks that are currently active or scheduled in the app. You can read about this feature in the "Async-aware debugging"
  
• Better exception support for Windows Runtime components. In Windows 8.1, exceptions that arise from Windows Store apps preserve information about the error that caused the exception, even across language boundaries. You can read about this feature in the "Windows Store app development" section of the
  

• What's new in the .NET Framework 4.5.2
  

  
  

  • New APIs for ASP.NET apps. The new HttpResponse.AddOnSendingHeaders and HttpResponseBase.AddOnSendingHeaders methods let you inspect and modify response headers and status code as the response is being flushed to the client app. Consider using these methods instead of the PreSendRequestHeaders and PreSendRequestContent events; they are more efficient and reliable.
    The HostingEnvironment.QueueBackgroundWorkItem method lets you schedule small background work items. ASP.NET tracks these items and prevents IIS from abruptly terminating the worker process until all background work items have completed. This method can't be called outside an ASP.NET managed app domain.
    The new HttpResponse.HeadersWritten and HttpResponseBase.HeadersWritten properties return Boolean values that indicate whether the response headers have been written. You can use these properties to make sure that calls to APIs such as HttpResponse.StatusCode (which throw exceptions if the headers have been written) will succeed.
    
  • Resizing in Windows Forms controls. This feature has been expanded. You can now use the system DPI setting to resize components of the following additional controls (for example, the drop-down arrow in combo boxes):