.NET CLR Interview Questions and Answers

Question 1. What is the .NET Framework?

Answer: The .NET is a Framework, which is a collection of classes of reusable libraries given by Microsoft to be used in other .NET applications and to develop, build and deploy many types of applications on the Windows platform including the following:

• Console Applications
• Windows Forms Applications
• Windows Presentation Foundation (WPF) Applications
• Web Applications
• Web Services
• Windows Services
• Services-oriented applications using Windows Communications Foundation (WCF)
• Workflow-enabled applications using Windows Workflow Foundation(WF)

That primarily runs on the Microsoft Windows Operating System.

• .NET Framework Overview

Question 2. What is CLR?

Answer: The CLR stands for Common Language Runtime and it is an Execution Environment. It works as a layer between Operating Systems and the applications written in .NET languages that conform to the Common Language Specification (CLS). The main function of Common Language Runtime (CLR) is to convert the Managed Code into native code and then execute the program. The Managed Code compiled only when it is needed, that is it converts the appropriate instructions when each function is called. The Common Language Runtime (CLR)’s just in time (JIT) compilation converts Intermediate Language (MSIL) to native code on demand at application run time.

When a .NET application is executed at that time the control will go to Operating System, the Operating System create a process to load CLR.

The program used by the operating system for loading CLR is called runtime host, which are different depending upon the type of application that is desktop or web-based application i.e.

The runtime host for desktop applications is an API function called CorbinToRuntime.

The runtime host for web-based applications is the ASP.NET worker process (aspnet-wp.exe).

CLR runtime engine comes with a set of services, which are classified as follows

CLR services

• Assembly Resolver
• Assembly Loader
• Type Checker
• COM marshaled
• Debug Manager
• Thread Support
• IL to native compiler
• Exception Manager
• Garbage Collector

To know more about them follow the link:

• Introduction to CLR in .NET framework

Question 3. What is CTS?

Answer: The Common Type System (CTS) standardizes the data types of all programming languages using .NET under the umbrella of .NET to a common data type for easy and smooth communication among these .NET languages.

To implement or see how CTS is converting the data type to a common data type, for example, when we declare an int type data type in C# and VB.NET, then they are converted to int32. In other words, now both will have a common data type that provides flexible communication between these two languages.

For more details follow the link:

• Common Type System (CTS) in .NET

Question 4. What is CLS?

Answer: One of the important goals of the .NET Framework is to Support Multiple Languages. This is achieved by CLS. For multiple languages to interoperate, it is necessary that they should go on in common in certain features such as Types that are used. For example, every language has its own size and range for different data types. Thus CLS is the agreement among language designers and class library designers concerning these usage conventions.

Follow the link for more details:

• What does .NET really mean? – Understanding .NET

Question 5. What is a managed code?

Answer: The resource, which is within your application domain is, managed code. The resources that are within the domain are faster.

The code, which is developed in the .NET framework, is known as managed code. This code is directly executed by CLR with help of managed code execution. Any language that is written in .NET Framework is managed code.

Managed code uses CLR which in turn looks after your applications by managing memory, handling security, allowing cross-language debugging, and so on.

For more details follow the link:

• Managed code and unmanaged code in .NET

Question 6. What is MSIL?

Answer: When we compile our .NET code then it is not directly converted to native/binary code; it is first converted into intermediate code known as MSIL code which is then interpreted by the CLR. MSIL is independent of hardware and the operating system. Cross-language relationships are possible since MSIL is the same for all .NET languages. MSIL is further converted into native code.

For more details follow the link:

• .Net Architecture and .Net Framework Basics

Question 7. What is JIT?

Answer: A Web Service or WebForms file must be compiled to run within the CLR. Compilation can be implicit or explicit. Although you could explicitly call the appropriate compiler to compile your Web Service or WebForms files, it is easier to allow the file to have complied implicitly. Implicit compilation occurs when you request the .asmx via HTTP-SOAP, HTTP-GET, or HTTP-POST. The parser (xsp.exe) determines whether a current version of the assembly resides in memory or in the disk. If it cannot use an existing version, the parser makes the appropriate call to the respective compiler (as you designated in the Class property of the .asmx page).

When the Web Service (or Web Forms page) is implicitly compiled, it is actually compiled twice. On the first pass, it is compiled into IL. On the second pass, the Web Service (now an assembly in IL) is compiled into machine language. This process is called Just-In-Time JIT compilation because it does not occur until the assembly is on the target machine.

JIT Types:

Follow the link for more details:

• JIT (Just-In-Time) Compiler

Question 8. What is a portable executable (PE)?

Answer: Every .NET program first compiles with an appropriate compiler like if we write a program in C# language then it gets compiled by C# compiler (i.e. csc.exe).

In the .NET framework, every program executes (communicate) in an operating system by using CLR (Common Language Runtime).

Managed module is standard windows Portable Executable (PE) file which contains the following parts.

• PE Header It is similar to the common object file format.
• CLR Header This contains the CLR version required to run this managed module, location & metadata. This also contains the entry point of function i.e. the address of the entry point of the function.
• Metadata This contains table information means variable with its data types and default values, functions/methods which are declared & defined in our program.

Follow the link for more details:

• C# Program Compilation Steps

Question 9. What is the application domain?

Answer: An Application Domain is a logical container for a set of assemblies in which an executable is hosted. As you have seen, a single process may contain multiple Application Domains, each of which is hosting a .NET executable. The first appdomain created when the CLR is initialized is called the default AppDomain and this default one is destroyed when the Windows process is terminated.

• An AppDomain can be independently secured.
• An AppDomain can be unloaded.
• Independently configured.
• No mutual intervention by multiple appdomains.
• Performance