Assemblies. necessary and sufficient to make that file self describing. This unit is called Assembly.

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Todd Jackson
6 years ago
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1 Assemblies Any.NET application written by a developer may be a component that is designed to provide some service to other applications or itself a main application. In both cases when that.net application is compiled to MSIL code, the language compiler produces a COFF based composite file that contains not only MSIL code but all other information that is necessary and sufficient to make that file self describing. This unit is called Assembly. Assembly is a file or a set of files containing MSIL code and resources supporting that code. 74

2 C# Windows or Console Application.EXE File Assembly C# Class Library.dll File An assembly is the fundamental unit of code on.net Platform. 75

3 Assembly Structure t Assembly may be a single file [Single File Assembly] or composition of several files [Composite F.A.]. Single File Assembly Composite File Assembly Type Metadata Manifest Type Metadata MSIL Code Resources Manifest Type Metadata MSIL Code Resources MSIL Code Type Metadata MSIL Code 76

4 Manifest Each assembly either it is single file assembly or composite file assembly contain manifest. Manifest contains information about modules in assembly and references to other assemblies. In single file assembly there is only one physical file that contains all four pieces of information. Composite file assembly is a logical unit in which only one file contains manifest and that manifest contains the references to other files and its regular information. These other files contain MSIL code for a different module along with its type metadata. 77

5 Type Metadata t The metadata acts in two ways: as a table of contents, describing what is contained inside the assembly and as a bibliography describing references to data outside the assembly. Type metadata provides information about the code. It provides the description of members (classes, properties, methods etc.) present with in the code of assembly along with the data types for their parameters and return values. 78

6 MSIL Code MSIL is the CPU-independent instruction set into which the.net Framework programs are compiled. MSIL includes instructions for loading, storing, initializing and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. 79

7 Resources These are the Non-Executable parts or files required in the code such as images, icons or text files. These take part in execution, but passively. Are as much of importance as the live active code. 80

8 Assembly Types Static Assembly: Static assembly can include.net Framework Types (Interfaces & Classes), as well as resources for the assembly(bitmaps, JPEG files, resource files, and so on). Static assemblies are stored on disk in PE files. Dynamic assembly: The.NET framework can also create dynamic assemblies, which are run directly from the memory and are not saved to disk before execution. We can store dynamic assemblies to disk after they have executed. 81

9 Pi Private &Shared dassembly Private Assemblies: The assembly that is used as a part of single application, is called private assembly. Private assembly must be stored in the same directory as the application. By default an assembly is private to the user application. 82

10 Limitations of being a private assembly An application, in general, requires services of one or more assemblies (components). To use them, reference is given to those assemblies in the calling code. If those are private assemblies, and are not present in calling applications directory, the first thing it requires is to copy all those assemblies into the active application directory, before being used. This solution had two major shortcoming: First unnecessary storing copies of a single assembly in multiple directories, which are part of same application. Second, the copy of original assembly may not be consistent. To remove this shortcoming,.net provided the concept of Shared Assemblies. 83

11 Shared Assemblies An assembly is made to be shared assembly so that any program on that system can use it as a component. A program does not need to know the location of the shared assembly. This is because shared assemblies are registered in a.net system special directory called the Global Assembly Cache (GAC). 84

12 Assembly Cache An assembly cache is machine-wide code cache used for side by side storage of assemblies. There are two parts to the cache: Global Assembly Cache (GAC): It contains assemblies that are explicitly installed to be shared among many applications on the computer. GAC is a special directory located in the windows\assembly directory on Windows XP or WINNT\assembly directory on Windows 2000/2003. All shared assemblies including the.net Framework System assemblies supplied by Microsoft.NET Framework Library are located and loaded in Cache. Download Cache: It stores code downloaded from Internet on Intranet sites, isolated to the application that triggered the download so that code downloaded on behalf of one application or page does not impact the other applications. 85

13 Benefits of Assembly Independence from system registry Solving Versioning Problem (DLL HELL) Assembly = MSIL + Metadata Metadata is binary information describing the program that is stored either in a CLR PE File or in memory. During compilation of the code into a PE file, metadata is inserted into one portion of the file, while the code is converted to MSIL and inserted to another portion of the file. Every type and member defined and referenced in a module or assembly is described d in a language-neutral l manner within metadata. When the code is executed, Runtime loads metadata into memory and references it to discover information about the code s classes, members, inheritance and so on. 86

14 Benefits of metadata Key to simpler programming model, eliminating need for Interface Definition Language files, header files, or any other external method of component reference. Implements highest level of abstraction. Extensible through h use of attributes. t No registration required with OS, self-describing. Supports automatic language interoperabilitity without explicit marshaling or using custom interoperability code. Attributes: specific kind of metadata, used to control how program behaves at run time. Developer can emit own custom-metadata into.net Framework files through user-defined custom Attributes. 87

Authoring Installations for Microsoft s.net Framework

Authoring Installations for Microsoft s.net Framework using Wise for Windows Installer Vanessa Wasko Wise Solutions, Inc. Abstract This paper provides an overview of creating an installation for an application