All Dotnet Interview Questions 1-50

Question 1 - What Is CLR ? 

CLR is Common Language Runtime is the runtime that converts a MSIL code into the host machine language code. It is the execution engine for .NET Framework applications. It provides a number of services, including:

·         Code management (loading and execution)

·         Memory Management

·         Thread Management

·         Conversion of IL to native code.

·         Access to metadata (enhanced type information)

·         Managing memory for managed objects (Garbage collection)

·         Enforcement of code access security (Security Management)

·         Exception handling, including cross-language exceptions

·         Interoperation btw managed code, COM objects, and pre-existing DLL's (unmanaged code and data)

·         Support for developer services (profiling, debugging, and so on).

·         Type safety.

Question 2 - What is CLR HOST?

A CLR host is an application that is responsible for loading the CLR into a process, creating application domains within the process, and executing user code within the application domains.

Examples of hosts that ship with the .NET Framework include:

·         ASP.Net - An ISAPI filter that ships with ASP.NET loads the CLR and does the initialization necessary to handle web requests.

·         Internet Explorer: - A MIME filter hooks into IE versions 5.01 and higher to execute managed controls referenced from HTML pages.

Question 3 - What is CTS?

CTS is Common Type System, which describes how types are declared, used and managed. CTS facilitate cross-language integration, type safety, and high performance code execution.

Example in VB you have “Integer” and in C++ you have “long” these data types are not compatible so the interfacing between them is very complicated. In order that these two different languages communicate Microsoft introduced Common Type System. So “Integer” data type in VB and “int” data type in C++ will convert it to System.int32, which is data type of CTS.

Question 4 - What is CLS?

CLS Is Common Language Specification, is a specification that defines the rules to support language integration. This is done in such a way, that programs written in any language (.NET compliant) can interoperate with one another. This also can take full advantage of inheritance, polymorphism, exceptions, and other features. It was always a dream of Microsoft to unite all different languages in to one umbrella and CLS is one-step towards that.

Question 5 - What is an Intermediate Language?

(IL) Intermediate Language Or (CIL) Common Intermediate Language Or (MSIL) Microsoft Intermediate Language, is one of the Core component of the .NET Framework. Any .NET source codes written in any .net supportive language (C#,VB.net etc), when compiled are converted to MSIL. This MSIL, when installed or at the Runtime, gets converted to machine code. The Runtime conversion of MSIL code to the machine code is handled by a component called as the Just In Time (JIT) Compiler.

Question 6 - What is Just In Time Compiler?

It is a compiler which converts MS IL (Microsoft Intermediate Language) code to Native Code (i.e. CPU-specific code that runs on the same computer architecture). Just-In-Time compiler- it converts the language that you write in .Net into machine language that a computer can understand. There are 3 types of JITs

·         Pre-JIT compiler (Compiles entire code into native code completely in a single Operation)

·         Econo JIT compiler (Compiles only methods(Code) called at Runtime)

·         Normal JIT compiler (Compiles only that part of code called at Runtime and places in cache)

Question 7 - What is Portable executable (PE)?

The file format defining the structure that all executable files (EXE) and Dynamic Link Libraries (DLL) must use to allow them to be loaded and executed by Windows. Windows PE is divided into 2 main sections.

·         The first section includes the PE/COFF headers that references the contents within the PE file.

·         The second section is the native image section which contains .data, .rdata, .rsrc, and .text sections.

Question 8 - What is Managed Code?

Managed code runs inside the environment of CLR i.e. .NET runtime. In short, all IL are managed code. However, if you are using some third party software example VB6 or VC++ component they are unmanaged code, as .NET runtime (CLR) does not have control over the source code execution of these languages.

A runtime-aware compiler compiles the IL into native executable code within a managed execution environment that ensures type safety, array bound and index checking, exception handling, and garbage collection. Also, many unproductive programming tasks are automatically taken care of, such as type safety checking, memory management, and destruction of unneeded objects. You can therefore focus on the business logic of your applications and write them using fewer lines of code. The result is shorter development time and more secure and stable applications.

Question 9 - What is UnManaged Code?

As mentioned above the Unmanaged code will be one where

·         The CLR cannot able to understand the code.

·         The CLR cannot instruct the code.

·         The second time compilation is unmanaged code. It is understood only by the machine not by the user.

Question 10 - What is Garbage Collector?

Garbage collection is a process of releasing the memory used by the objects, which are no longer referenced. This is done in different ways and different manners in various platforms and languages.

When an program is loaded in the memory there will be a bunch of memory allocated for that particular program alone and loaded with memory. This bunch of memory is called Managed Heap(is nothing but a bunch of memory allocated for the program at run time). This amount of memory will only be used when an object is to be loaded in to the memory for that particular program.
This memory is separated in to three parts:

·         Generation Zero – Smaller size

·         Generation One – Medium size

·         Generation Two – Larger size

When we try to create an object by using NEW keyword the system will,

·         Calculate the number of bytes required for the object or type to be loaded in to the managed heap.

·         The CLR then checks that the bytes required to allocate the object are available in the reserved region. IF the object fits, it is allocated at the address pointed to by NextObjPtr.

·         These processes will happen at the Generation zero level.

Question 11 - What is a Strong Name?

A strong name is a .NET assembly name combined with its version number and other information to uniquely identify the assembly. This allows multiple versions of the same assembly to peacefully co-exist in the global assembly cache, where shared assemblies are typically stored. It consists of five parts as mentioned below

·         Simple Name – Usually the name of the file (without the extension) that contains the assembly

·         Public Key – RSA cryptographic public key that helps verify the assembly's authenticity

·         Version – Four-part version number, in the form of Major.Minor.Build.Revision

·         Culture – Target audience for the assembly, such as "neutral" (default audience), "en-us" (English – United States) or "fr" (France) etc.

·         Processor Architecture – Defines the assembly's format, such as MSIL (intermediate language) or x86 (binary for Intel x86 processors)

Question 12 - What are the steps to create Strong Name?

We have a set of steps that should be followed to create a strong name as shown below.

·         Open .net command prompt.

·         Go to the folder containing DLL.

·         Type sn -k test.snk, This will create  test .snk file in that folder.

·         Open the assemblyinfo.cs file of project.

·         Type file path  in this tag [assembly:AssemblyKeyFile@"E:\Code\practice\HP\bin\Debug\HP.snk")]

·         Build  application, finally your strong name created for your DLL.

Question 13 - What are the Problems faced using Strong Name?

·         Requires Exact Match. If you use strong names, your application or library must load the assembly with the exact strong name that you specify, including version and culture.

·         Cannot Lose Private Key. If your private key is lost or stolen, the security of your assembly is compromised. You will be forced to re-issue a new assembly signed with a new public-private key pair.

Question 14 - What is Program Database?

A program database files holds debugging and project state information that allows incremental linking of debug configuration of your program. A PDB file can be up to 2GB.

Question 15 - What is Delay Signing?

It is signing an assembly with its strong name public key, which is freely distributable, instead of using the private key as usual. This allows developers to use and test a strong-named assembly without access to the private key. Then at a later stage (typically just before shipping the assembly), a manager or trusted key holder must sign the assembly with the corresponding private key.

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Question 16 - What is an Assembly?

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.

Question 17 - What are the Contents of an Assembly

·         Type metadata.

·         The assembly manifest, which contains assembly metadata.

·         Microsoft intermediate language (MSIL) code that implements the types.

·         A set of resources

Question 18 - What are the Types of an Assemblies?

Assemblies are of four types

·         Private - The assembly is intended only for one application

·         Shared - If the assembly is to be made into a Shared Assembly(GAC)

·         Static – These are the .NET PE files that you create at compile time. 

·         Dynamic - These are PE-formatted, in-memory assemblies that you dynamically create at runtime

Question 19 - What is a Satellite assembly?

·         A .NET Framework assembly containing resources specific to a given language.

·         Using satellite assemblies, you can place the resources for different languages in different assemblies.

·         The correct assembly is loaded into memory only if the user elects to view in that language.

·         Culture is maintained in a text file which acts like a resource to the assembly.

Question 20 - What are the Steps to Create Satellite Assembly?

Below are the steps to create a satellite assembly

·         Set the paths for resgen and al.exe:

·         Create a .resources file.

·         Create the satellite assembly.

·         The assembly should have the naming convention for .NET to be able to search for it. 

·         Specify the settings for culture.

·         Put the satellite assembly in the appropriate folder.

·         Once the satellite assembly is created, physically copy it to the appropriate directory. 

·         Repeat the process for each language in which you are creating an assembly.

 Question 21 - What is an Assembly Loader? 

·         Checks if the assembly is Strongly signed.

·         If yes it will search in the GAC

·         Loader will search the policy file name in the format of

·         Policy.AssemblyMajorVersion.AssemblyMinorVersion.AssemblyName

·         Eg. MyPolicy.1.2.Assembly1

·         If such a file exists it will look inside of it if the version of the assembly that we are trying to load matches the version/versions range written in the policy file. If it does, it will try to load the assembly with the version specified there. If no such policy file exists, it will try to load assembly from the GAC.

·         If it will fail to find it in the GAC, it will start to search in the system’s search path.
In web applications it will also include the application’s Bin directory in the search path.

Question 22 - What is Multi Module Assembly or Assembly Linker? 

We like to combine Hello.dll with GoodBye.dll and put them into a Private Assembly we call GreetAssembly.dll.

DotNet> al /t:library /out:bin\Hellowroldassembly.dll bin\GoodDay.dll bin\GoodMorning.dll

For this purpose we use the Assembly Linker. As /t (target) we generate here a library referencing the two other DLLs. This is also called a Multi-Module Assembly. Again, we store all the binaries in a bin folder.

Question 23 - What is an Assembly Manifest? 

The assembly manifest contains this assembly metadata. An assembly manifest contains all the metadata needed to specify the assembly's version requirements and security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a standalone PE file that contains only assembly manifest information.

Question 24 - What is a Metadata? 

Metadata is data that describes the state of the assembly and a detailed description of each type, attribute within the assembly. Metadata stores the following information:

·         Description of the assembly.

§  Identity (name, version, culture, public key).

§  The types that are exported.

§  Other assemblies that this assembly depends on.

§  Security permissions needed to run.

·         Description of types.

§  Name, visibility, base class, and interfaces implemented.

§  Members (methods, fields, properties, events, nested types).

·         Attributes.

§  Additional descriptive elements that modify types and members.

Question 25 - What is a Base class in .Net?

Base class is the one from which the object and references are being inherited in .net

·         System.object is for .Net

·         System.Web.UI is for asp.net

Question 26 - What is Full Assembly Reference?

A full assembly reference includes the assembly's text name, version, culture, and public key token (if the assembly has a strong name). A full assembly reference is required if you reference any assembly that is part of the common language runtime or any assembly located in the global assembly cache.

Question 27 - What is Partial Assembly Reference?

We can dynamically reference an assembly by providing only partial information, such as specifying only the assembly name. When you specify a partial assembly reference, the runtime looks for the assembly only in the application directory.

Question 28 - What is an Assembly Qualified Name?

An assembly qualified name isn't the filename of the assembly; it's the internal name of the assembly combined with the assembly version, culture, and public key, thus making it unique.

Question 29 - What is ILDASM (Intermediate Language Disassembler)?

It is a tool provided in C# to view and read the assembly content in manifest view. This tool is supplied along with the Visual Studio .NET you are using. It is also available along with .NET SDK. To access this tool, you have to run the ildasm.exe

Question 30 - What is Global Assembly Cache? 

·         The GAC stores assemblies specifically designated to be shared by several applications on the computer.

·         Assemblies deployed in the GAC must have a strong name.

·         When an assembly is added to the GAC, 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.

·         Use a developer tool called the Global Assembly Cache tool (Gacutil.exe), provided by the .NET Framework SDK or Use Windows Explorer to drag assemblies into the cache.

Question 41 - What is Custom Serialization?

·         In some cases, the default serialization techniques provided by .NET may not be sufficient in real life.

·         This is when we require implementing custom serialization.

·         It is possible to implement custom serialization in .NET by implementing the ISerializable interface.

·         This interface allows an object to take control of its own serialization and de-serialization process.

·         It gives us a great deal of flexibility in the way we can save and restore objects.

Question 42 - What is a Namespace?

·         Containers of objects which contain classes, unions, structures, interfaces, enumerators, delegates.

·         Main goal is for creating hierarchical organization of program.

·         Developers does not need to worry about the naming conflicts of classes, functions, variables etc.

Question 43 - What is GUID?

It is Short form of Globally Unique Identifier,

A unique 128-bit number that is produced by the Windows OS or Windows app to identify a particular component, application, file, database entry, and/or user.

Question 44 - What is a Formatter?

·         A formatter is used to determine the serialization format for objects.

·         In other words, it is used to control the serialization of an object to and from a stream.

·         They are the objects that are used to encode and serialize data into an appropriate format before they are transmitted over the network.

·         They expose an interface called the IFormatter interface. IFormatter's significant methods are Serialize and De-serialize which perform the actual serialization and de-serialization.

·         There are two formatter classes provided within .NET, the BinaryFormatter and the SoapFormatter. Both these classes extend the IFormatter interface.

Question 45 - What is a Binary Formatter?

The Binary formatter provides support for serialization using binary encoding. The BinaryFormater class is responsible for binary serialization and is used commonly in .NET's Remoting technology. This class is not appropriate when the data is supposed to be transmitted through a firewall.

 Question 46 - What is a SOAP Formatter?

The SOAP formatter provides formatting that can be used to serialize objects using the SOAP protocol. It is used to create a Soap envelop and it uses an object graph to generate the result. It is responsible for serializing objects into SOAP messages or parsing the SOAP messages and extracting these serialized objects from the SOAP messages. SOAP formatters in .NET are widely used by the Web Services.

Question 47 - What is Reflection?

·         It is a collection of classes which allow u to query assembly (class/object) metadata at runtime.

·         Using reflection we can also create new types and their instances at runtime and invoke methods on these new instances.

·         At runtime, the Reflection mechanism uses the PE file to read information about the assembly.

·         We can dynamically invoke methods using System.Type.Invokemember

·         We can dynamically create types at runtime using System.Reflection.Emit.TypeBuilder

·         With reflection we can do the below

§  we can dynamically create an instance of a type

§  bind the type to an existing object

§  get the type from an existing object

§  invoke its methods or access its fields and properties

Question 48 - What is Thread and Process?

·         Threads are basically light weight processes responsible for multitasking within a single application.

·         The base class used for threading is System.Threading.

·         Threads are implemented when situations in which you want to perform more than one task at a time.

§  A Process is an instance of a running application.

§  A thread is the Execution stream of the Process.

§  A process can have multiple Threads.

·         Example: A Microsoft Word is an Application. When you open a word file, an instance of the Word starts and a process is allocated to this instance which has one thread.

§  Create Thread – use System.Thread() class and create an instance.

§  Join Thread - use object.Join() to join threads.

§  Suspend Thread - use object.Sleep(<No of seconds>) to suspend a thread.

§  Kill Thread - use object.Abort() to abort a thread.

Question 49 - What are the difference between a Dll and an Exe?

DLL	EXE
Create an object of dll	Not in exe
In Process Component	Out Process Component
Multiple Uses	Single use
Cannot be started as stand alone	Can be started as stand alone

Question 50 - What are Globalization and Localization?

To implementing a multilingual user interface, you design the user interface to open in the default UI language and offer the option to change to other languages. Globalization is the first step in the process. A globalized application supports localized user interfaces and regional data for all users. Truly global applications should be culture-neutral and language-neutral. A globalized application can correctly accept, process, and display a worldwide assortment of scripts, data formats, and languages. Accommodating these cultural differences in an application is called localization.