Chapter 1:- Introduction to.net. Compiled By:- Ankit Shah Assistant Professor, SVBIT.

Transcription

1 Chapter 1:- Introduction to.net Compiled By:- Assistant Professor, SVBIT.

2 What is.net? 2 Microsoft s vision of the future of applications in the Internet age Increased robustness over classic Windows apps New programming platform Built for the web.net is a platform that runs on the operating system

3 .NET 3 Sits on top on the OS (currently all the Windows; Linux/Unix subset also available Mono Project) About 20MB download Provides language interoperability across platforms Strong emphasis on Web connectivity, using XML web services to connect and share data between smart client devices, servers, and developers/users Platform/language independent

4 History 4 Development began in 1998 Beta 1 released Oct, 2000 Beta 2 released July, 2001 Finalized in Dec, shipping in Feb 2002

5 .NET Overview 5 Three main elements: The Framework (CLR, FCL, ASP, WinForms) The Products (Windows, Visual Studio, Office) The Services (My Services) Framework Goals Improved reliability and integrated security. Simplified development and deployment. Unified API, multi-language support. All MS server products now.net-enabled.

6 Cont d 6 The.Net framework is a service or platform for building, developing and running application The.Net consists of 2 main parts: Common language runtime (CLR) Class libraries (FCL)

7 .NET Framework 7 C# VB.NET C++.NET Other Common Language Specification Framework Class Library ASP.NET Windows Forms Web Services Web Forms Controls Drawing ASP.NET Application Services Windows Application Services Visual Studio.NET ADO.NET XML Threading IO Network Security Diagnostics Etc. Common Language Runtime Memory Management Common Type System Lifecycle Monitoring Operating System

8 8.NET Framework

9 Common Language Runtime (CLR) 9 Multi-language runtime environment Over 21 languages supported today Managed Execution Environment Secure Code Execution Language/Hardware/OS Independent Compact Framework for Small Devices

10 (CLR) Cont d 10 It is the execution engine for.net framework application. It is the heart or backbone of the.net It is the runtime engine provided by the.net framework. It provides an infrastructure for run program and allows them to communicate with other parts of the.net framework. It provides no. of services: Code loading and execution Manage code, Exception handling Cross-language exception.

11 (CLR) Cont d 11 The CLR loads, executes and manages code that has been compiled into an intermediate byte-code format called Microsoft Intermediate Language (MSIL). This code is not interpreted it is compiled to native binary code before execution by just-in-time (JIT) compilers built into CLR. Two levels of compilers in.net The source code compiles => MSIL This MSIL byte code is portable to any.net platform At execution time then compile by the JIT compilers into binary code.

12 Managed code and Unmanaged 12 code in.net.net supports two kind of coding Managed Code Unmanaged Code

13 Cont d... (Managed Code) 13 The resource, which is with in your application domain is, managed code. The resources that are within domain are faster. The code, which is developed in.net framework, is known as managed code. This code is directly executed by CLR with help of managed code execution. Any language that is written in.net Framework is managed code. Managed code uses CLR which in turns looks after your applications by managing memory, handling security, allowing cross - language debugging, and so on.

14 14

15 Cont d... (Unmanaged Code) 15 The code, which is developed outside.net, Framework is known as unmanaged code. Applications that do not run under the control of the CLR are said to be unmanaged, and certain languages such as C++ can be used to write such applications, which, for example, access low - level functions of the operating system. Background compatibility with code of VB, ASP and COM are examples of unmanaged code. Unmanaged code is executed with help of wrapper classes. Wrapper classes are of two types: CCW (COM Callable Wrapper) and RCW (Runtime Callable Wrapper).

16 16

17 17

18 MSIL 18 MSIL code is CPU and platform-independent. It can be executed in any environment that supports the CLR.

19 .NET Framework Class Library (FCL) 19 Framework you can call it and it can call you Large class library Over 2500 classes Major components Base Class: Networking, security, I/O, files, etc. Data and XML Classes Web Services/UI Windows UI

20 Framework Libraries 20 Web Services Expose application functionalities across the Internet, in the same way as a class expose services to other classes. Each Web service can function as an independent entity, and can cooperate with one another. Data described by XML. ASP.NET Replacement for the Active Server Technology. Web Forms provide an easy way to write interactive Web applications, much in the same way as normal Windows applications.

21 Framework Libraries 21 Provides facilities to generate Windows GUI-based client applications easily Form-oriented Standard GUI components buttons, textboxes, menus, scrollbars, etc. Event-handling

22 Common Language Specification (CLS) 22 CLS is a set of rules that specifies features that all languages should support Goal: have the.net framework support multiple languages CLS is an agreement among language designers and class library designers about the features and usage conventions that can be relied upon Example: public names should not rely on case for uniqueness since some languages are not case sensitive This does not mean all languages are not case sensitive above the CLR! Common Type System (CTS) CTS allows program written in different programming language to easily share information. CTS provides cross language integration.

23 Some.NET Languages 23 C# COBOL Eiffel Fortran Mercury Pascal Python Perl Smalltalk VB.NET VC++.NET J#.NET Scheme. More are planned or under development

24 VB.NET and C# 24 VB.NET introduces long sought-after features: Inheritance Parameterized Class Constructors Function Overloading Multi-Threading Structured Error Handling Creating NT Services VB.NET not backward compatible with VB6. C# New modern, object-oriented language Similar to C++/Java Considered the most powerful language of.net

25 .NET vs. J2EE 25 Both are similar in many ways: Server- and client-side model for building enterprise applications. Virtual machine designed to inspect, load, and execute programs in a controlled environment. APIs for creating both fat- and thin-client models. APIs for foundation services (data access, directory, remote object calls, sockets, forms). Development environment for dynamic web pages. J2 Enterprise Edition Language-Dependent & Platform-Independent.NET Language-Independent & Platform Dependent (Not now)

26 26 J2EE: Language-Specific, Platform- Independent Person.java Linux Java VM Person bytecodes Java VM Deploy Windows Address bytecodes Company bytecodes Java VM Address.java Company.java Solaris Java VM

27 .NET: Language-Independent, 27 (Mostly) Platform- Specific Person.vb (Visual Basic) Windows CLR Person MSIL CLR Deploy Windows Address MSIL Company MSIL CLR Others? Address.cs (C#) Company.cbl CLR (Cobol)

28 J2EE 28 The core (JVM and standard class libraries) are mature. 3-4 million Java programmers. J2EE implementations are not entirely crossplatform. Java s true potential is realized only when all (or most) development is done in Java. Changing the Java language specification has an enormous impact on the entire platform.

29 .NET 29.NET built into Windows; running an executable invokes the CLR automatically instead of explicitly invoking the JVM Being newer,.net added improvements such as native XML support, new features to CLR About 3 million C++ developers, 3-8 million VB developers, around 1 million C# developers Today, most development and deployment is Windows

30 The Common Type System (CTS) or Common Lang. Implementation (CLI) 30 At the core of the Framework is a universal type system called the.net Common Type System (CTS). Everything is an object - but efficient Boxing and Unboxing All types fall into two categories - Value types and Reference types. Value types contain actual data (cannot be null). Stored on the stack. Always initialized. Three kinds of value types: Primitives, structures, and enumerations. Language compilers map keywords to the primitive types. For example, a C# int is mapped to System.Int32.

31 The Common Type System (CTS) 31 Reference types are type-safe object pointers. Allocated in the managed heap Four kinds of reference types: Classes, arrays, delegates, and interfaces. When instances of value types go out of scope, they are instantly destroyed and memory is reclaimed. When instances of reference types go out of scope, they are garbage collected. Boxing = converting an instance of a value type to a reference type. Usually done implicitly through parameter passing or variable assignments. UnBoxing = casting a reference type back into a value type variable.

32 The Common Type System 32 Object String Array ValueType Exception Delegate Class1 Int16 Int32 Boolean Byte Enum Multicast Delegate Class2 Class3 Int64 Char Single Currency Double DateTime Decimal TimeSpan Primitive Types

33 MSIL and JIT Compilation 33 Source code is compiled into MSIL (Microsoft Intermediate Language). Similar to Java bytecodes - CPU-independent instructions MSIL allows for runtime type-safety and security, as well as portable execution platforms. The MSIL architecture results in apps that run in one address space - thus much less OS overhead. Compilers also produce metadata or glue that binds the code with debuggers, browsers, etc. Definitions of each type in your code. Signatures of each type s members. Members that your code references. Other runtime data for the CLR.

34 MSIL and JIT Compilation 34 Metadata in the load file along with the MSIL enables code to be self-describing - no need for separate type libraries, IDL, or registry entries. When code is executed by the CLR, a JIT compilation step occurs. Code is compiled method-by-method to native machine code as methods are invoked Results in performance slowdown when a program is first executed, but can be efficient for code that is never executed Subsequent invocations reuse compiled code, so no slowdown

35 JIT 35 It stands for just in time. It s a smart compiler. JIT does not compile whole program each time and every time. It compile only that portion of the program which functions are called that time. And suppose native code is already present then that data will not again compiled. If changes are made then possible that it will again generate MSIL to native. Firstly any program compile by its own compiler then it will convert into MSIL then with the help of the JIT; MSIL compile into native code but CLR does not convert whole MSIL code to native code on Load time of that application; instead of it compiles the MSIL instruction as they are called.

36 Cont d 36 There are 3 type of JIT. Pre-JIT It compiles complete program into native code in a single compilation cycle. This process is done at the time of deployment of the program. Econo-JIT It compiles only those methods that are called at runtime. Normal-JIT It s like econo-jit. The methods that are compiled the 1st time they are stored in cache. When the same methods are called again the compiled code from cache is used for execution.

37 Delegates 37 A new concept that is central to the programming model of the CLR. Delegates are like function pointers, but are actually typesafe, secure, managed CLR objects. The CLR guarantees that a delegate points to a valid method. You get the benefits of function pointers without the dangers. Each delegate is based on a single method signature. Commonly used for callbacks. Delegates are basis of event handlers.

38 Packaging: Modules, Types, 38 Assemblies, and the Manifest A module refers to a managed binary, such as an EXE or DLL. Modules contain definitions of managed types, such as classes, interfaces, structures, and enumerations. An assembly can be defined as one or more modules that make up a unit of functionality. An assembly is the fundamental unit of deployment, version control, activation scoping, and security permissions.

39 Packaging: Modules, Types, 39 Assemblies, and the Manifest An assembly is a set of boundaries: A security boundary - the unit to which permissions are requested and granted. A type boundary - the scope of an assembly uniquely qualifies the types contained within. A reference scope boundary - specifies the types that are exposed outside the assembly. A version boundary - all types in an assembly are versioned together as a unit. Avoid multiple version problem for DLL s

40 Packaging: Modules, Types, 40 Assemblies, and the Manifest An assembly contains a manifest, which is a catalog of component metadata containing: Assembly name. Version (major, minor, revision, build). Assembly file list - all files contained in the assembly. Type references - mapping the managed types included in the assembly with the files that contain them. Scope - private or shared. Referenced assemblies. In many cases, an assembly consists of a single EXE or DLL - containing the module s MSIL, the component metadata, and the assembly manifest. In other cases, the assembly may consist of many DLLs, with the manifest in its own file. No MSIL code can ever be executed unless there is a manifest associated with it.

41 Assemblies (What is assembly?) 41 An assembly is the primary building block of a.net framework application. An assembly is a logical DLL. It consists of DLLs or executables. It is a collection of functionality that is built, versioned and deployed as a single implementation unit. A private assembly is used only by a single application, and is stored in that application s install directory A shared assembly is one that can be referenced by more than one application.

42 MetaData (What is metadata?) 42 Metadata stores within the assembly. Metadata means data about data. A.Net language compiler will generate the metadata and stores this in the assembly. On the.net platform programs are compiled into.net PE(portable executable )files. Metadata is nothing but a description of every namespace, class, method, property etc. contained within the PE file. The CLR uses this metadata to Locate classes, Load classes, Generate native code, Provide security

43 What is.net framework class 43 library? In C, <conio.h> etc. are header files. We add those header files in our program to use inbuilt function. Same hear, the.net framework are collection of classes or namespace that can be used to develop application. The class library consist of data classes, XML classes, web forms classes and window forms based classes, smart device classes, input-output classes. Other name of FCL is BCL(Base class library)

44 What is namespace? 44 As above, the.net framework class library is collection of namespace. Namespace is a logical naming scheme for types that have related functionality. Namespace is nothing but a logical container or partition. It s like drive of out computer. Like my computer contain C:, D:, E:, F: my F: drive contains songs and video and C: contains installed file so on. For example my friend wants songs. So I will directly go to my computer s F: because songs are places there.

45 Cont d 45 As the root of the hierarchy is the system namespace. The notion of a namespace plays a fundamental role in the.net framework. Common namespace: System Contains fundamental classes and base classes. System.Data Contains system classes for database connection. System.IO Contains classes for reading and writing data in file.

46 Garbage Collection 46 Garbage collection is a mechanism that allows the computer to detect when an object can no longer be accessed. It then automatically free up the memory used by that object. One of the advantages of CLR is automatic memory management that uses the garbage collection mechanism. The CLR s garbage collector GC manages the allocation and release of memory for an application.

47 Metadata 47 Metadata is machine-readable information about a resource, or data about data. Such information might include details on content, format, size, or other characteristics of a data source. In.NET, metadata includes type definitions, version information, external assembly references, and other standardized information.

48 Meta Data 48 Metadata provides enough information for any runtime, tool, or program to find out literally everything that is needed for component integration. CLR Class loader Just-in-time (JIT) compilers Tools

49 Intermediate Language (IL) 49 In software engineering, the concept of abstraction is extremely important. We often use abstraction to hide the complexity of system or application services, providing instead a simple interface to the consumer. In language advances, scientists introduced different incarnations of language abstraction layers, such as p-code and bytecode. Produced by the Pascal-P compiler, p-code is an intermediate language that supports procedural programming. Generated by Java compilers, bytecode is an intermediate language that supports object-oriented programming. Bytecode is a language abstraction that allows Java code to run on different operating platforms, as long as the platforms have a Java Virtual Machine (JVM) to execute bytecode.

50 Cont d 50 Microsoft calls its own language-abstraction layer the Microsoft Intermediate Language (MSIL) or IL, for short. Similar to bytecode, IL supports all object-oriented features, including data abstraction, inheritance, polymorphism, and useful concepts such as exceptions and events. In addition to these features, IL supports other concepts, such as properties, fields, and enumeration. Any.NET language may be converted into IL, so.net supports multiple languages and multiple platforms, as long as the target platforms have a CLR.

51 51

52 Versioning 52 There are four types of assemblies in.net: Static assemblies These are the.net PE files that you create at compile time. Dynamic assemblies These are PE-formatted, in-memory assemblies that you dynamically create at runtime using the classes in the System.Reflection.Emit namespace. Private assemblies These are static assemblies used by a specific application. Shared assemblies These are static assemblies that must have a unique shared name and can be used by any application.

53 Cont d 53 An application uses a private assembly by referring to the assembly using a static path or through an XML-based application configuration file. It ensures that an application uses the correct shared assemblies with which the application was built. Thus, an application uses a specific shared assembly by referring to the specific shared assembly, and the CLR ensures that the correct version is loaded at runtime.

54 Side-by-Side Execution 54 The CLR allows any versions of the same, shared DLL (shared assembly) to execute at the same time, on the same system, and even in the same process. This concept is known as side-by-side execution. Microsoft.NET accomplishes side-by-side execution by using the versioning and deployment features that are innate to all shared assemblies. This concept allows you to install any versions of the same, shared assembly on the same machine, without versioning conflicts or DLL Hell.

55 Side by Side Execution 55

56 Cont d 56 The only thing is that your assemblies must be public or shared assemblies, meaning that you must register them against the GAC using a tool such as the.net Global Assembly Cache Utility (gacutil.exe). Once you have registered different versions of the same shared assembly into the GAC, the human-readable name of the assembly no longer matters what s important is the information provided by.net s versioning and deployment features.

57 Execution Support and Management 57 Garbage collection Exception handling Security support Debugging support Interoperation support (COM InterOp) The CLR supports interoperation between the managed (CLR) and unmanaged (no CLR) worlds. The COM Interop facility serves as a bridge between COM and the CLR, allowing a COM object to use a.net object, and vice versa. The Platform Invoke (P/Invoke) facility allows you to call Windows API functions.

58 Features of.net 58 Ease of deployment and configuration Strong XML support No more DLL Hell Automatic memory management Security Multi-Device Support Multi-Language Support OOPs Support Easy development of web applications Rich Functionality out of the box

59 Features of.net 59 Rich Functionality out of the box.net framework provides a rich set of functionality out of the box. It contains hundreds of classes that provide variety of functionality ready to use in your applications. This means that as a developer you need not go into low level details of many operations such as file IO, network communication and so on. Easy development of web applications ASP.NET is a technology available on.net platform for developing dynamic and data driven web applications. ASP.NET provides an event driven programming model (similar to Visual Basic 6 that simplify development of web pages (now called as web forms) with complex user interface. ASP.NET server controls provide advanced user interface elements (like calendar and grids) that save lot of coding from programmer s side.

60 Features of.net (Cont d ) 60 OOPs Support The advantages of Object Oriented programming are well known..net provides a fully object oriented environment. The philosophy of.net is Object is mother of all. Languages like Visual Basic.NET now support many of the OO features that were lacking traditionally. Even primitive types like integer and characters can be treated as objects something not available even in OO languages like C++. Multi-Language Support

61 Features of.net (Cont d ) 61 Multi-Device Support Modern life style is increasingly embracing mobile and wireless devices such as PDAs, mobiles and handheld PCs....NET provides promising platform for programming such devices..net Compact Framework and Mobile Internet Toolkit are step ahead in this direction. Automatic memory management While developing applications developers had to develop an eye on system resources like memory. Memory leaks were major reason in failure of applications..net takes this worry away from developer by handling memory on its own. The garbage collector takes care of freeing unused objects at appropriate intervals.

62 Features of.net (Cont d ) 62 No more DLL Hell If you have worked with COM components, you probably are aware of DLL hell. DLL conflicts are a common fact in COM world. The main reason behind this was the philosophy of COM one version of component across machine. Also, COM components require registration in the system registry..net ends this DLL hell by allowing applications to use their own copy of dependent DLLs. Also,.NET components do not require any kind of registration in system registry. Strong XML support.net is the only platform that has built with XML right into the core framework..net tries to harness power of XML in every possible way. In addition to providing support for manipulating and transforming XML documents,.net provides XML web services that are based on standards like HTTP, XML.

63 Features of.net (Cont d ) 63 Ease of deployment and configuration Deploying windows applications especially that used COM components were always been a tedious task. Since.NET does not require any registration as such, much of the deployment is simplified. Security Windows platform was always criticized for poor security mechanisms. Microsoft has taken great efforts to make.net platform safe and secure for enterprise applications. Features such as type safety, code access security and role based authentication make overall application more robust and secure.

64 Reflection 64 The process of getting the metadata from modules/assemblies. When.NET code is compiled, metadata about the types defined in the modules is produced. These modules are in turn packaged as assemblied. The process of accessing this metadata at runtime is called Reflection. The namespace System.Reflection contains classes that can be used for interrogating the types for a module/assembly. We use reflection for examining data type sizes for marshalling across process & machine boundaries. Reflection is also used for: 1)To dynamically invoke methods (using System.Type.InvokeMember) 2) To dynamically create types at runtime (usingsystem.reflection.emit.typebuilder).