.NET Framework (Part I)

(B)What is a IL?
Twist :- What is MSIL or CIL , What is JIT?
(IL)Intermediate Language is also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code is compiled to IL. This IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In- Time (JIT) compiler.

(B)What is a CLR?
Full form of CLR is Common Language Runtime and it forms the heart of the .NET framework.All Languages have runtime and its the responsibility of the runtime to take care of the code execution of the program.For example VC++ has MSCRT40.DLL,VB6 has MSVBVM60.DLL , Java has Java Virtual Machine etc. Similarly .NET has CLR.Following are the responsibilities of CLR:

√ Garbage Collection :- CLR automatically manages memory thus eliminating
memory leakes. When objects are not referred GC automatically releases those memory thus providing efficient memory management.
√ Code Access Security :- CAS grants rights to program depending on the security configuration of the machine.Example the program has rights to edit or create a new file but the security configuration of machine does not allow the program to delete a file.CAS will take care that the code runs under the environment of machines security configuration.
√ Code Verification :- This ensures proper code execution and type safety while the code runs.It prevents the source code to perform illegal operation such as accessing invalid memory locations etc.
√ IL( Intermediate language )-to-native translators and optimizer’s :- CLR uses JIT and compiles the IL code to machine code and then executes. CLR also determines depending on platform what is optimized way of running the IL code.

(B)What is a CTS?
In order that two language communicate smoothly CLR has CTS (Common Type System).Example in VB you have “Integer” and in C++ you have “long” these datatypes are not compatible so the interfacing between them is very complicated. In order that two different languages can communicate Microsoft introduced Common Type System. So “Integer” datatype in VB6 and “int” datatype in C++ will convert it to System.int32 which is datatype of CTS.CLS which is covered in the coming question is subset of CTS.

If you have undergone COM programming period interfacing VB6 application with VC++ application was a real pain as the datatype of both languages did not have a common ground where they can come and interface , by having CTS interfacing is smooth.

(B)What is a CLS(Common Language Specification)?
This is a subset of the CTS which all .NET languages are expected to support.It was always a dream of microsoft to unite all different languages in to one umbrella and CLS is one step towards that.Microsoft has defined CLS which are nothing but guidelines that language to follow so that it can communicate with other .NET languages in a seamless manner.

(B)What is a Managed Code?
Managed code runs inside the environment of CLR i.e. .NET runtime.In short all IL are managed code.But if you are using some third party software example VB6 or VC++ component they are unmanaged code as .NET runtime (CLR) does not have control over the source code execution of the language.

(B)What is a Assembly ?
√ Assembly is unit of deployment like EXE or a DLL.

√ An assembly consists of one or more files (dlls, exe’s, html files etc.), and
represents a group of resources, type definitions, and implementations of those types. An assembly may also contain references to other assemblies. These resources, types and references are described in a block of data called a manifest. The manifest is part of the assembly, thus making the assembly self-describing.

√ An assembly is completely self-describing.An assembly contains metadata information, which is used by the CLR for everything from type checking and security to actually invoking the components methods.As all information is in
assembly itself it is independent of registry.This is the basic advantage as compared to COM where the version was stored in registry.

√ Multiple versions can be deployed side by side in different folders. These different versions can execute at the same time without interfering with each other.Assemblies can be private or shared. For private assembly deployment,the assembly is copied to the same directory as the client program that references it.No registration is needed, and no fancy installation program is required. When the component is removed, no registry cleanup is needed,and no uninstall program is required. Just delete it from the hard drive.

√ In shared assembly deployment, an assembly is installed in the Global Assembly Cache (or GAC). The GAC contains shared assemblies that are globally accessible to all .NET applications on the machine.

(A) What are different types of Assembly?
There are two types of assembly Private and Public assembly.A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. Crystal report classes which will be used by all application for Reports..
(B) What is NameSpace?
Namespace has two basic functionality :-
√ NameSpace Logically group types.Example System.Web.UI logically groups our UI related features.
√ In Object Oriented world may times its possible that programmers will use the same class name.By qualifying NameSpace with classname this collision can be removed.

(B) What is Difference between NameSpace and Assembly?
Following are the differences between namespace and assembly :
√ Assembly is physical grouping of logical units. Namespace logically groups classes.
√ Namespace can span multiple assembly.

(A)If you want to view a Assembly how to you go about it ?
Twist : What is ILDASM ?
When it comes to understanding of internals nothing can beat ILDASM.ILDASM basically converts the whole exe or dll in to IL code.To run ILDASM you have to go to "C:\Program Files\Microsoft Visual Studio .NET 2003\SDK\v1.1\Bin". Note that i had v1.1 you have to probably change it depending on the type of framework version you have.
If you run IDASM.EXE from the path you will be popped with the IDASM exe program as shown in figure ILDASM.Click on file and browse to the respective directory for the DLL whose assembly you want to view.After you select the DLL you will be popped with a tree view details of the DLL as shown in figure ILDASM.On double clicking on manifest you will be able to view details of assembly , internal IL code etc as shown in Figure Manifest View.

Note : The version number are in the manifest itself which is defined with the DLL or EXE thus making deployment much easier as compared to COM where the information was stored in registry.Note the version information in Figure Manifest view.

You can expand the tree for detail information regarding the DLL like methods etc.

(A) What is Manifest?
Assembly metadata is stored in Manifest.Manifest contains all the metadata needed to do the following things( See Figure Manifest View for more details):
√ Version of assembly
√ Security identity
√ Scope of the assembly
√ resolve references to resources and classes.
√ The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a stand-alone PE file that contains only assembly manifest information

Continue to Part II