Hi All,

This is a list of questions I have gathered from other sources and created myself over a period of time from my experience, many of which I felt where incomplete or simply wrong.  I have finally taken the time to go through each question and correct them to the best of my ability.  However, please feel free to post feedback to challenge, improve, or suggest new questions.  I want to thank those of you that have contributed quality questions and corrections thus far.

General Questions

Does C# support multiple-inheritance?
No.
 
Who is a protected class-level variable available to?
It is available to any sub-class (a class inheriting this class).
 
Are private class-level variables inherited?
Yes, but they are not accessible.  Although they are not visible or accessible via the class interface, they are inherited.
 
Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
 
What’s the top .NET class that everything is derived from?
System.Object.
 
What does the term immutable mean?
The data value may not be changed.  Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
 
What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable.  System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
 
What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation.  Strings are immutable, so each time a string is changed, a new instance in memory is created.
 
Can you store multiple data types in System.Array?
No.
 
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array.  The CopyTo() method copies the elements into another existing array.  Both perform a shallow copy.  A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array.  A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.
 
How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
 
What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
 
What class is underneath the SortedList class?
A sorted HashTable.
 
Will the finally block get executed if an exception has not occurred?­
Yes.

What happens in memory when you Box and Unbox a value-type?
Boxing converts a value-type to a reference-type, thus storing the object on the heap.  Unboxing converts a reference-type to a value-type, thus storing the value on the stack.

Thanks Arjun for such a valuable question bank.

Here is one point I got stuck in my application

Why does my Windows application pop up a console window every time I run it?

Thanks in advance

Hi dear,

You can check that the target type set in the project properties setting is set to Windows Application, and not Console Application. If you’re using the command line, compile with /target:winexe, not /target:exe.

Hope this will be useful to you.:(

Same problem with my application.. how to check compilation mode?

plz help

thankx in advance

Hi Arjun.

I wanted to add some more basic questions asked in most interviews.

What is a Delegate?
A strongly typed function pointer. A delegate object encapsulates a reference to a method. When actual function needs to be called will be decided at run-time.

Static Variable and Its Life-Time:
VB.NET: Public Shared VAR As Type.
C#: public static Type VAR;
Life time is till the class is in memory.

Constructor:
Special Method Always called whenever an instance of the class is created.

Destructor/Finalize:
Called by GC just before object is being reclaimed by GC.

 

ASP.Net

Different Types of Caching?
Output Caching: stores the responses from an asp.net page.
Fragment Caching: Only caches/stores the portion of page (User Control)
Data Caching: is Programmatic way to Cache objects for performance.

Authentication and Authorization:
Authentication is identifying/validating the user against the credentials (username and password) and Authorization performs after authentication. Authorization allowing access of specific resource to user.

Different Types of Directives:
Page, Register, Control, OutputCache, Import, Implements, Assembly, Reference

Difference between Server-Side and Client-Side:
Server-Side code is executed on web-server and does not transmitted to client, while client-side code executed on client(browser) and is rendered to client along with the content.

Difference Server.Transfer and Response.Redirect:
Both ends the processing for the current request immediately. Server.Transfer start executing the another resource specified as parameter without acknowledgement to client(browser) while Response.Redirect intimate client that your requested resource is available at this location and then client request for that resource.

Different Types of Validators and Validation Controls:
RequiredFieldValidator, RangeValidator, RegularExpressionValidator, CompareValidator, CustomValidator, ValidationSummary

How to Manage State in ASP.Net?
Client based: ViewState, QueryString and Cookies Server based: Session, Application.

Difference between User Control and Custom Control:
CUSTOM Controls are compiled code (Dlls), easier to use, difficult to create, and can be placed in toolbox. Drag and Drop controls. Attributes can be set visually at design time. Can be used by Multiple Applications (If Shared Dlls), Even if Private can copy to bin directory of webApp add reference and use. Normally designed to provide common functionality independent of consuming Application.

3 Types of Session State Modes?
InProc(cookieless, timeout),
StateServer (Server, Port stateConnectionString="tcpip=server:port"),
SQLServer (sqlconnectionstring) and Off.

What is ViewState and How it is managed, Its Advantages/Benefits?
ViewState is a special object that ASP.NET uses to maintain the state of page and all webcontrols/ServerControls within it. It is in this object preserves the states of various FORM elements during post-backs. It is rendered to client(browser) as a Hidden variable __VIEWSTATE under <form>tag. We can also add custom values to it.

What is web.config and machine.config:
machine.config is default configuration for all applications running under this version, located in %WinDir%\Microsfot.Net\Framework\Version. Settings can be overridden by Web.Config for an specific application Web.Config resides in application’s root/virtual root and exists in sub-sequent folders.

Role of Global.asax:
Optional file contains the code to handle Application level events raised by ASP.Net or By HttpModule. This file resides in application root directory. Application_Start, _End, _AuthenticateRequest, _Error, Session_Start, _End, BeginRequest, EndRequest. This file is parsed and compiled into dynamically generated class derived from HttpApplication.

Page Life Cycle:
Init, LoadViewState, LoadPostBackData, Load, RaisePostBackDataChangedEvent, RaisePostBackEvents, Pre-Render, SaveViewState, Render, Unload, (IpostBackDataChangedEventHandler and IpostBackEventHandler) Error, CommitTransaction, AbortTransaction, Abort
inetinfo.exe, aspnet_isapi.dll aspnet_wp.exe, HttpModules (OutputCache, Session, Authentication, Authorization, Custom Modules Specified) and Then HttpHandlers PageHandlerFactory for *.aspx

Can the action attribute of a server-side <form>tag be set to a value and if not how can you possibly pass data from a form to a subsequent Page?
No assigning value will not work because will be overwritten at the time of rendering. We can assign value to it by register a startup script which will set the action value of form on client-side. Rest are Server.Transfer and Response.Redirect.

ASP.Net List Controls and differentiate between them?
RadioButtonList, CheckBoxList, DropDownList, Repeater, DataGrid, DataList

Type Of Code in Code-Behind class:
Server-Side Code. 


 

Hi Arjun

    About the multiple Inheritance in C# ...

There is a slight catch here.as you can implement it in C# but using Interfaces...you can use at most one instantiating class while inherting but the no os Interfaces could be of any number.... This is very handy at the design time when the Design of the modules gets fixed to implement certain functionality in the subsequent modules. 

Hi Somender,

Yeah , it support through Interface. Anyway thanxs and congratulation to have such catchy eyes. :)

Cheer!

HI Arjun, tnx for such a good matterial for interview.That will help me for my prepration for cracking the interview.

Thnx once again...

i m lookin forwars for more question.hope i will get more from you..

cya

Manjeet

Software Developer. 

Hi, Manjeet

Here's some qestions related to Assembly. Hope it will do some favour to you.

1. How is the DLL Hell problem solved in .NET?
   Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly. 
    
2. What are the ways to deploy an assembly?
   An MSI installer, a CAB archive, and XCOPY command. 
    
3. What is a satellite assembly?
   When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies. 
    
4. What namespaces are necessary to create a localized application?
   System.Globalization and System.Resources.
    
5. What is the smallest unit of execution in .NET?
   an Assembly.
    
6. When should you call the garbage collector in .NET?
   As a good rule, you should not call the garbage collector.  However, you could call the garbage collector when you are done using a large object (or set of objects) to force the garbage collector to dispose of those very large objects from memory.  However, this is usually not a good practice.
    
7. How do you convert a value-type to a reference-type?
   Use Boxing.
    
8. What happens in memory when you Box and Unbox a value-type?
   Boxing converts a value-type to a reference-type, thus storing the object on the heap.  Unboxing converts a reference-type to a value-type, thus storing the value on the stack.

Good Luck.

1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?
   Value.  The data type of the value parameter is defined by whatever data type the property is declared as. 
    
2. What does the keyword “virtual” declare for a method or property?
   The method or property can be overridden. 
    
3. How is method overriding different from method overloading?
   When overriding a method, you change the behavior of the method for the derived class.  Overloading a method simply involves having another method with the same name within the class. 
    
4. Can you declare an override method to be static if the original method is not static?
   No.  The signature of the virtual method must remain the same.  (Note: Only the keyword virtual is changed to keyword override) 
    
5. What are the different ways a method can be overloaded?
   Different parameter data types, different number of parameters, different order of parameters. 
    
6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
   Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
   

How do I send out simple debug messages to help with my debugging?

Debug.Write("Hello, Debugger!");

bool @this = true;
bool that = false;
Debug.WriteLineIf(@this || that, "A conditional Hello!");

using System.IO;
        
public string GetTempPath()
{
    string path = System.Environment.GetEnvironmentVariable("TEMP");
    if (!path.EndsWith("\\")) path += "\\";
    return path;
}

public void LogMessageToFile(string msg)
{
    System.IO.StreamWriter sw = System.IO.File.AppendText(
        GetTempPath() + "My Log File.txt");
    try
    {
        string logLine = System.String.Format(
            "{0:G}: {1}.", System.DateTime.Now, msg);
        sw.WriteLine(logLine);
    }
    finally
    {
        sw.Close();
    }
}

LogMessageToFile("Hello, World");

What does the /target: command line option do in the C# compiler?

What is the difference between const and static readonly?

How do I create a constant that is an array?

const int [] constIntArray = newint [] {2, 3, 4};
 // error CS0133: The expression being assigned to 'constIntArray' must be constant
const int [] constIntArrayAnother = {2, 3, 4};
 // error CS0623: Array initializers can only be used in a variable or field
 //               initializer. Try using a new expression instead. 

static readonly int [] constIntArray = new int[] {1, 2, 3};

[Flags]
public enum Role
{
	Administrator = 1,
	BackupOperator = 2,
	// etc. 
}

public class RoleAttribute : Attribute
{
	public RoleAttribute()
	{
		CreateRole = DefaultRole;
	}

	public RoleAttribute(Role role)
	{
		CreateRole = role;
	}

	public Role CreateRole
	{
		get { return this.createRole; }
		set { this.createRole = value; }
	}

	private Role createRole = 0;
	public const Role DefaultRole = Role.Administrator
	 | Role.BackupOperator;
}

[RoleAttribute(RoleAttribute.DefaultRole)]
public class DatabaseAccount
{
	//.............. 
}

Add Custom .NET Assemblies to the Add Reference Dialog

Hi Guys . Thanks alot for providing such a valuable information in here..

its really a great help...

can anyone tell me something about REFLECTIONS in .net

I need that infor right away....

Hi Sonia,

Reflection is the ability to read metadata at runtime. Using reflection, it is possible to uncover the methods, properties, and events of a type, and to invoke them dynamically. Reflection also allows us to create new types at runtime, but in the upcoming example we will be reading and invoking only.

Reflection generally begins with a call to a method present on every object in the .NET framework: GetType. The GetType method is a member of the System.Object class, and the method returns an instance of System.Type. System.Type is the primary gateway to metadata. System.Type is actually derived from another important class for reflection: the MemeberInfo class from the System.Reflection namespace. MemberInfo is a base class for many other classes who describe the properties and methods of an object, including FieldInfo, MethodInfo, ConstructorInfo, ParameterInfo, and EventInfo among others. As you might suspect from thier names, you can use these classes to inspect different aspects of an object at runtime.