Web Services

1. What are Windows services?
   Windows services, previously known as NT services, are applications that are installed on the system as system services. In other words, Windows services are applications that run in the background with the Windows operating system. The primary use of Windows services is to reduce the consumption of memory required for performing backend operations. Let's take an example to understand this easily. Suppose you want to perform a variety of functions, such as monitor the performance of your computer or application, check the status of an application, and manage various devices, such as printers. 

   
   

   In such a case, you can use Windows services to reduce memory consumption. In addition, Windows services can run on your system even if you have not logged on to your computer. In addition, these services do not have any user interface.
2. Can you share a process between Windows services?
   Yes, you can share a process between Windows services.
3. In .NET, which is the parent class to create all Windows services?
   The ServiceBase class is the parent class to create all Windows services.

Dynamic Programming

1. What is Dynamic Language Runtime (DLR)?
   DLR is a runtime environment that allows you to integrate dynamic languages with the Common Language Runtime (CLR) by adding a set of services, such as expression trees, call site caching, and dynamic object interoperability to the CLR. 

   
   

   The System.Dynamic and System.Runtime.CompilerServices namespaces are used to hold the classes for DLR. It also provides dynamic features to statically-typed languages, such as C# and Visual Basic to enable their interoperation with dynamic languages.
2. What are the advantages of DLR?
   The various advantages provided by DLR are:

   • Allows you to easily implement the dynamic languages to the .NET Framework.
   • Provides dynamic features to statically-typed languages. The statically-typed .NET Framework languages, such as C# and Visual Basic can create dynamic objects and use them together with statically-typed objects.
   • Implements sharing of libraries and objects, which means that the objects and libraries implemented in one language can be used by other languages using DLR. The DLR also enables interoperation between statically-typed and dynamic languages.
   • Enables fast execution of dynamic operations by supporting advance caching.
3. Give a brief introduction to Binders.
   Binders are used by DLR to communicate with not the .NET Framework but also with various other services, such as Silverlight and COM. These services represent language-specific semantics and specify how a particular operation can be performed at the call site.

   
   

   Call sites refer to the area in the code where logical and mathematical operations, such as a + b or a.b() are performed on dynamic objects.
4. Explain the different services provided by DLR to CLR.
   The services provided by DLR to CLR are used for supporting dynamic languages. These services include the following:

   • Expression Trees - Refers to the representation of code in a data structure similar to a tree. However, expression trees in DLR are the advanced version of the expression trees that were introduced with LINQ in .NET 3.5. Therefore, DLR has extended the functionalities of Language Integrated Query (LINQ) expression trees, such as control flow, assignment, and other language-modeling nodes to a dynamic language. These expression trees define the semantics of a language in form of an abstract syntax tree (AST). AST enables the DLR to dynamically generate code, which the CLR executes at runtime.
   • Call Site Caching - Enables the DLR to store the information of the operations and characteristics of the variables, such as their data type. The call site caching services also enables to check whether such operations have been performed previously to retrieve all the information about the variable. The place where DLR stores these values is called a call site.