ASP.NET Interview questions ?

Interview questions 

What are differences between Array list and Hash table?

Ans: 1) Hash table store data as name, value pair. While in array only value is store.
2) To access value from hash table, you need to pass name. While in array, to access value, you need to pass index number.
3) you can store different type of data in hash table, say int, string etc. while in array you can store only similar type of data.

What are differences between system.stringbuilder and system.string?

The main difference is system.string is immutable and system.stringbuilder is a mutable. Append keyword is used in string builder but not in system.string.
Immutable means once we created we cannot modified. Suppose if we want give new value to old value simply it will discarded the old value and it will create new instance in memory to hold the new value.



What are the differences between Application object and session object?

Ans: The session object is used to maintain the session of each user. If one user enter in to the application then they get session id if he leaves from the application then the session id is deleted. If they again enter in to the application they get different session id.
But for application object the id is maintained for whole application.

What are the different types of indexes?

Ans: Two types of indexes are there one is clustered index and non-clustered index

How many types of memories are there in .net? 

Ans: Two types of memories are there in .net stack memory and heap memory

Is it possible to set the session out time manually? 

Ans: Yes we can set the session out time manually in web.config.

What are differences between function and stored procedure?

Ans:
1) Function returns only one value but procedure returns one or more than one value.
2) Function can be utilized in select statements but that is not possible in procedure.
3) Procedure can have an input and output parameters but function has only input parameters only.
4) Exceptions can be handled by try catch block in procedures but that is not possible in function.

What are the differences between Abstract and interface?

Ans:  1) Abstract cannot be instantiated but we can inherit. Interface it cannot be inherit it can be instantiate
2) Interface contain only declarations no definitions. Abstract contain declarations and definitions.
3) The class which contains only abstract methods is interface class. A class which contains abstract method is called abstract class
4) Public is default access specifier for interface we don’t have a chance to declare other specifiers. In abstract we have chance to declare with any access specifier

Can you Explain Page lifecycle in .net?
Can you Explain .NET architecture in .net?

What is the difference between primary key and unique key with not null?

Ans: There is no difference between primary key and unique key with not null.

What is boxing and unboxing concepts in .net? 

Ans: Boxing is a process of converting value type into reference type
Unboxing is a process of converting reference type to value type.

What are the differences between value type and reference type?

Ans: Value type contain variable and reference type are not containing value directly in its memory.
Memory is allocated in managed heap in reference type and in value type memory allocated in stack. Reference type ex-class value type-struct, enumeration

Is it possible to host the website from desktop?

Ans: Yes

Why we go for page rendering in Asp.Net Page life cycle?

Ans: Browser understands an only html control that’s why in page rendering we will convert the aspx controls into html controls.

Write a sample query for self join?

Ans: Select e1.ename, e2.empid from emp e1, emp e2 where e1.empid=e2.mgrid;

Can we change the index of primary key on table?

Ans: No

How to change the name of the table or stored procedure in sql?

Ans: sp_rename oldtablename newtablename
For changing the column name
Sp_rename  ‘tablename.[Oldcolumnname]’,’newcolumnname’,’Column’
Ex:sp_rename ‘tblemp.first’,’namechange’,’Column’

How to find out which index is defined on table?

Ans: sp_helpindex tablename

Can you write the program to find the length of string without using library function?

Ans: for (int i=0; str[i]!=”\n”; i++)
{
Count++;
}

What is the difference between scope_identity() and current_identity()?

Ans: Scope_identity and current _identity both are similar and it will return the last identity value generated in the table.
Scope_Identity will return the identity value in table that is currently in scope

What are difference between GET and POST Methods?

Ans:
GET Method ():

1) Data is appended to the URL.
2) Data is not secret.
3) It is a single call system
4) Maximum data that can be sent is 256.
5) Data transmission is faster
6) this is the default method for many browsers

POST Method ():

1) Data is not appended to the URL.
2) Data is Secret
3) it is a two call system.
4) There is no Limit on the amount of data. That is characters any amount of data can be sent.
5) Data transmission is comparatively slow.
6) No default and should be explicitly specified.

What are difference between truncate and delete?

Ans: 1) Delete keep the lock over each row where Truncate keeps the lock on table not on all the row.
2) Counter of the Identity column is reset in Truncate where it is not reset in Delete.
3) Trigger is not fired in Truncate where as trigger is fired in Delete.
4) In TRUNCATE we cannot rollback.
5) In DELETE we can rollback

What is the difference Grid View and between Data Grid (Windows)?

Ans:
1) GridView Control Enables you to add sorting, paging and editing capabilities without writing any code.
2)GridView Control Automatically Supports paging by setting the ‘PagerSetting’ Property.The Page Setting Property supports four Modles

a. Numeric(by default)
b. Next Previous
c. NumericFirstLast
d. Next PreviousLast

3)It is Used in asp.net
4)GridView Supports RowUpdating and RowUpdated Events.
5)GidView is Capable of Pre-Operations and Post-Operations.
6)GridView Has EditTemplates for this control
7)It has AutoFormat

DataGrid(Windows)

1)DataGid Control raises single Event for operations
2)DataGird Supports the SortCommand Events that occur when a column is Soted.
3)DataGrid Supports UpdataCommand Event that occurs when the UpdateButton is clicked for an item in the grid.
4)DataGrid is used in Windows GUI Application.
5)It doesnot have EditTemplates for this control
6)It doesnot have AutoFormat

If I write System.exit (0); at the end of the try block, will the finally block still execute?

Ans: No in this case the finally block will not execute because when you say system.exit(0),the control immediately goes out of the program, and thus finally never executes.

What are the different levels of State management in ASP.NET?

Ans:
State management is the process by which you maintain state and page information over multiple requests for the same or different pages.

There are 2 types State Management:

1. Client – Side State Management
This stores information on the client's computer by embedding the information into a Web page, a uniform resource locator (url), or a cookie. The techniques available to store the state information at the client end are listed down below:

a. View State – Asp.Net uses View State to track the values in the Controls. You can add custom values to the view state. It is used by the Asp.net page framework to automatically save the values of the page and of each control just prior to rendering to the page. When the page is posted, one of the first tasks performed by page processing is to restore view state.

b. Control State – If you create a custom control that requires view state to work properly, you should use control state to ensure other developers don’t break your control by disabling view state.

c. Hidden fields – Like view state, hidden fields store data in an HTML form without displaying it in the user's browser. The data is available only when the form is processed.

d. Cookies – Cookies store a value in the user's browser that the browser sends with every page request to the same server. Cookies are the best way to store state data that must be available for multiple Web pages on a web site.

e. Query Strings - Query strings store values in the URL that are visible to the user. Use query strings when you want a user to be able to e-mail or instant message state data with a URL.

2. Server – Side State Management
a. Application State - Application State information is available to all pages, regardless of which user requests a page.

b. Session State – Session State information is available to all pages opened by a user during a single visit.

Both application state and session state information is lost when the application restarts. To persist user data between application restarts, you can store it using profile properties.

Abstract Class:

Abstract class is a class which can’t be instantiate. Class should have “Abstract” key word with the name.  In any one of the method of class having abstract method with in it, then it should be define as abstract class. The class which derived the abstract class should have definition of the abstract method. These classes which derived the abstract class and implement the abstract methods call concrete class.
Abstract class may have the definition of function or may not.  Below is the simple example of an abstract class
public abstract alass AbstractStudent
    {
        String Roll
        {
            get;
            set;
        }

        String FirstName
        {
            get;
            set;
        }
     
        String LastName
        {
            get;
            set;
        }
     

        Public String GetStudentDetails()
             {

                  // Implementation of Method  
             }

        public String SaveStudentDetails ()
            {
                  // Implementation of Method  
             }

        public abstract String CalculateWage();

    }
So, the class having one abstract method so we need to mention the class as "abstract" .

Difference between Abstract Class and Interface?

Abstract class is a class which can’t be instantiated and which can have methods with definition as well as declaration also. This can be inherited.

As for Example:

public abstract class AbstractStudent
    {
        String Roll
        {
            get;
            set;
        }

        String FirstName
        {
           get;
           set;
        }
 
        String LastName
        {
           get;
            set;
        }

        Public String GetStudentDetails()
            {
                 // Implementation of Method
             }

        public String SaveStudentDetails ()
            {
                  // Implementation of Method
            }

        public abstract String CalculateWage();

    }


Interface can only contain the methods declaration and can be implemented in the class.

As for Example:
Public interface IStudnet
    {
        String Roll
        {
           get;
            set;
        }

        String FirstName
        {
            get;
            set;
        }
 
        String LastName
        {
            get;
            set;
        }
 
        String GetStudentDetails();
        String SaveStudentDetails ();
    }

Below are the few main difference between Abstract Class and Interface

a.    In abstract class method can have definition as well as declaration also. But Interface should have only definition.
b.    All the Methods are Public as default and don’t have any access Modifier Controls in interface, whereas for abstract class we can have access modifier for methods.
c.    Abstract class can have constructor or destructor, whereas interface not.
d.    Abstract class can’t be part of multiple inheritance and we can implement multiple interface.

What do you mean by String objects are immutable?

String objects are immutable as its state cannot be modified once created. Every time when we perform any operation like add, copy, replace, and case conversion or when we pass a string object as a parameter to a method a new object will be created.

Example:
String str = "ABC";

str.Replace("A","X");

Here Replace() method will not change data that "str" contains, instead a new string object is created to hold data "XBC" and the reference to this object is returned by Replace() method.

So in order to point str to this object we need to write below line.
str = str.Replace("A","X");
Now the new object is assigned to the variable str. earlier object that was assigned to str will take care by garbage collector as this one is no longer in used.

What is dll hell problem in .NET and how it will solve?

Ans: Dll hell, is kind of conflict that occurred previously, due to the lack of version supportability of dll for (within) an application
.NET Framework provides operating system with a global assembly cache. This cache is a repository for all the .net components that are shared globally on a particular machine. When a .net component installed onto the machine, the global assembly cache looks at its version, its public key and its language information and creates a strong name for the component. The component is then registered in the repository and indexed by its strong name, so there is no confusion between the different versions of same component, or DLL

What is a Partial class?

Ans: Instead of defining an entire class, you can split the definition into multiple classes by using partial class keyword. When the application compiled, c# compiler will group all the partial classes together and treat them as a single class. There are a couple of good reasons to use partial classes. Programmers can work on different parts of classes without needing to share same physical file
Ex:
Public partial class employee
{
Public void somefunction()
{
}
}
Public partial class employee
{
Public void function ()
{
}
}