Assemblies

Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations.

Difference between manifest , metadata?Manifest Maintains the information about the assemblies like version, name locale and an optional strong name that uniquely identifying the assembly. This manifest information is used by the CLR. The manifest also contains the security demands to verify this assembly. It also contains the names and hashes of all the files that make up the assembly. The .NET assembly manifest contains a cryptographic hash of different modules in the assembly. And when the assembly is loaded, the CLR recalculates the hash of the modules at hand, and compares it with the embeded hash. If the hash generated at runtime is different from that found in the manifest, .NET refuses to load the assembly and throws an exception.Metadata means Data about the data. metadata yields the types available in that assembly, viz. classes, interfaces, enums, structs, etc., and their containing namespaces, the name of each type, its visibility/scope, its base class, the interfaces it implemented, its methods and their scope, and each methods parameters, types properties, and so on. The assembly metada is generated by the high-level compilers automatically from the source files. The compiler embeds the metadata in the target output file, a dll, an .exe.Assemblies.assembly extern < assembly name > Specifies another assembly that contains items referenced by the current module (in this example, mscorlib)..publickeytoken < token > Specifies the token of the actual key of the referenced assembly. .ver < version number > Specifies the version number of the referenced assembly..assembly < assembly name > Specifies the assembly name..hash algorithm < int32 value > Specifies the hash algorithm used..ver < version number > Specifies the version number of the assembly..module < file name > Specifies the name of the modules that make up the assembly. In this example, the assembly consists of only one file..subsystem < value > Specifies the application environment required for the program. In this example, the value 3 indicates that this executable is run from a console..corflags Currently a reserved field in the metadata.

Assemblies are designed to simplify application deployment and to solve versioning problems .Assemblies Promote Code ReuseAssemblies Are Self-Describing

Assemblies can be deployed as private or shared. Private assemblies reside in the same directory (or possibly a subdirectory) as the client application making use of them. Shared assemblies, on the other hand, are libraries intended to be consumed by numerous applications on a single machine and are deployed to a specific directory termed the global assembly cache, or GAC.

Assemblies deployed in the global assembly cache must have a strong name. When an assembly is added to the global assembly cache, integrity checks are performed on all files that make up the assembly. The cache performs these integrity checks to ensure that an assembly has not been tampered with, for example, when a file has changed but the manifest does not reflect the change.A strong name consists of the assembly's identity its simple text name, version number, and culture information (if provided) plus a public key and a digital signature. You can ensure that a name is globally unique by signing an assembly with a strong name. There are several reasons why you might want to install an assembly into the global assembly cache: Shared location. File security. Side-by-side versioning. Additional search location.