Category: .NET

The misalignment of application layer objects to tables and rows is called impedance mismatch. Developers usually want a database which is easy to use. Relational databases save data in tables and rows, but our application hardly ever does.

class A{int x,string[] tags

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In the above example we have an object that contains a field x and tags, which contains a bunch of strings, or tags .If we want to save this data in a database we would need three tables one for main object, another for tags, and another to map tags to main object. This forces the developer to write a mapping layer or use an ORM to translate between object in our memory and what is saved in the database.

Garbage collector serves as a automatic memory manager. It allocates memory for objects on managed heap. The heap is divided into three generations, generation 0, generation 1 and generation 2 , so it can handle short-lived and long-lived objects. A temporary variable is an example of short-lived object and an object in server application with static data is an example of long lived object.

Generation 0 is youngest generation and contains short-lived objects. All newly created objects are contained in generation 0. Garbage collection occurs more frequently in this generation. If there is no memory in generation 0, they are promoted to generation 1.

Generation 1 acts as a buffer between short-lived and long-lived objects, it contains short-lived objects.

Generation 2 contains long lived objects.

• A marking phase will find and create a list of all live objects.
• A relocating phase will update the references to the objects that will be compacted.
• A compacting phase will reclaim the space occupied by the dead objects and will compact the surviving objects. The compacting phase will move objects that have survived a garbage collection toward the older end of the segment.

Managed code is not compiled to machine code but to an intermediate language which is interpreted and executed by some service(Common Language Runtime in case of .NET) on a machine and is therefore operating within a secure framework which handles dangerous things like memory and threads for us.

Unmanaged code is compiled to machine code and therefore executed by the Operating System directly.

Global assembly cache  (GAC) is a folder in windows directory to store the .NET assemblies that are specifically designated to be shared by all applications executed on a system. Assemblies can be shared among multiple applications on the machine by registering them in global assembly cache(GAC).

An Assembly is a “unit of deployment” for .NET ,almost always a .exe or .dll. A .NET assembly is a file that contains our compiled code, code that can execute under supervision of Common Language Runtime.

In C# terms its basically a single C# project.

Assemblies are 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 the type implementations. To the runtime, a type does not exist outside the context of an assembly.

• It would enable us to develop our application without having to free memory.
•  It allocates objects on managed heap efficiently.
•  It reclaims the objects that are no longer being used, clears their memory and keeps the memory available for future allocations.
•  It provides memory safety by making sure that an object cannot use the context of another object.