.Net Framwork Interview Question Part IV

31. What are Satellite Assemblies? How you will create this? How will you get the different language strings?

Ans. Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET Framework files are removed unless the last language for that .NET Framework version is being removed.
(For example, English and Japanese editions of the .NET Framework version 1.1 share the same core files. The Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources in a \ja subdirectory. An application that supports the .NET Framework version 1.1, regardless of its language, always uses the same core runtime files.)
http://www.ondotnet.com/lpt/a/2637

32. What is Assembly manifest? what all details the assembly manifest will contain?

Ans. Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the assembly relate to each other. 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.
It contains Assembly name, Version number, Culture, Strong name information, List of all files in the assembly, Type reference information, Information on referenced assemblies.

33. Difference between assembly manifest & metadata?

Ans. assembly manifest - An integral part of every assembly that renders the assembly self-describing. The assembly manifest contains the assembly's metadata. The manifest establishes the assembly identity, specifies the files that make up the assembly implementation, specifies the types and resources that make up the assembly, itemizes the compile-time dependencies on other assemblies, and specifies the set of permissions required for the assembly to run properly. This information is used at run time to resolve references, enforce version binding policy, and validate the integrity of loaded assemblies. The self-describing nature of assemblies also helps makes zero-impact install and XCOPY deployment feasible.
metadata - Information that describes every element managed by the common language runtime: an assembly, loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as well as security attributes, marshaling data, extended class and member definitions, version binding, and other information required by the runtime.

34. What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to public? Steps) How more than one version of an assembly can keep in same place?

Ans. Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. You should share assemblies by installing them into the global assembly cache only when you need to.
Steps
- Create a strong name using sn.exe tool
eg: sn -k keyPair.snk
- with in AssemblyInfo.cs add the generated file name
eg: [assembly: AssemblyKeyFile("abc.snk")]
- recompile project, then install it to GAC by either
drag & drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly) (shfusion.dll tool)
or
gacutil -i abc.dll

35. If I have more than one version of one assemblies, then how'll I use old version (how/where to specify version number?)in my application?

36. How to find methods of a assembly file (not using ILDASM)

Ans. Reflection

37. What is Garbage Collection in .Net? Garbage collection process?

Ans. The process of transitively tracing through all pointers to actively used objects in order to locate all objects that can be referenced, and then arranging to reuse any heap memory that was not found during this trace. The common language runtime garbage collector also compacts the memory that is in use to reduce the working space needed for the heap.

38. What is Reflection in .NET? Namespace? How will you load an assembly which is not referenced by current assembly?

Ans. All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).

39. What is Custom attribute? How to create? If I'm having custom attribute in an assembly, how to say that name in the code?

Ans. A: The primary steps to properly design custom attribute classes are as follows:
1. Applying the AttributeUsageAttribute ([AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)])
2. Declaring the attribute. (class public class MyAttribute : System.Attribute { // . . . })
3. Declaring constructors (public MyAttribute(bool myvalue) { this.myvalue = myvalue; })
4. Declaring properties
public bool MyProperty
{
get {return this.myvalue;}
set {this.myvalue = value;}
}
The following example demonstrates the basic way of using reflection to get access to custom attributes.
class MainClass
{
public static void Main()
{
System.Reflection.MemberInfo info = typeof(MyClass);
object[] attributes = info.GetCustomAttributes();
for (int i = 0; i < attributes.Length; i ++)
{
System.Console.WriteLine(attributes[i]);
}
}
}

Dot Net Interview Questions - Part 9

1. How do you implement postback with a text box? What is postback and usestate?
   Make AutoPostBack property to true
2. How can you debug an ASP page, without touching the code?
3. What is SQL injection?
   An SQL injection attack "injects" or manipulates SQL code by adding unexpected SQL to a query.
   Many web pages take parameters from web user, and make SQL query to the database. Take for instance when a user login, web page that user name and password and make SQL query to the database to check if a user has valid name and password.
   Username: ' or 1=1 ---
   Password: [Empty]
   This would execute the following query against the users table:
   select count(*) from users where userName='' or 1=1 --' and userPass=''
4. How can u handle Exceptions in Asp.Net?
5. How can u handle Un Managed Code Exceptions in ASP.Net?
6. Asp.net - How to find last error which occurred?
   A: Server.GetLastError();
   [C#]
   Exception LastError;
   String ErrMessage;
   LastError = Server.GetLastError();
   if (LastError != null)
   ErrMessage = LastError.Message;
   else
   ErrMessage = "No Errors";
   Response.Write("Last Error = " + ErrMessage);

7. How to do Caching in ASP?
A: <%@ OutputCache Duration="60" VaryByParam="None" %>

VaryByParam value	Description
none	One version of page cached (only raw GET)
*	n versions of page cached based on query string and/or POST body
v1	n versions of page cached based on value of v1 variable in query string or POST body
v1;v2	n versions of page cached based on value of v1 and v2 variables in query string or POST body

<%@ OutputCache Duration="60" VaryByParam="none" %>
<%@ OutputCache Duration="60" VaryByParam="*" %>
<%@ OutputCache Duration="60" VaryByParam="name;age" %>
The OutputCache directive supports several other cache varying options

• VaryByHeader - maintain separate cache entry for header string changes (UserAgent, UserLanguage, etc.)
• VaryByControl - for user controls, maintain separate cache entry for properties of a user control
• VaryByCustom - can specify separate cache entries for browser types and version or provide a custom GetVaryByCustomString method in HttpApplicationderived class
7. What is the Global ASA(X) File?

9. Any alternative to avoid name collisions other then Namespaces.
   A scenario that two namespaces named N1 and N2 are there both having the same class say A. now in another class i ve written
   using N1;using N2;
   and i am instantiating class A in this class. Then how will u avoid name collisions?
   Ans: using alias
   Eg: using MyAlias = MyCompany.Proj.Nested;
10. Which is the namespace used to write error message in event Log File?
11. What are the page level transaction and class level transaction?
12. What are different transaction options?
13. What is the namespace for encryption?
14. What is the difference between application and cache variables?
15. What is the difference between control and component?
16. You ve defined one page_load event in aspx page and same page_load event in code behind how will prog run?
17. Where would you use an IHttpModule, and what are the limitations of any approach you might take in implementing one?
18. Can you edit data in the Repeater control? Which template must you provide, in order to display data in a Repeater control? How can you provide an alternating color scheme in a Repeater control? What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?
19. What is the use of web.config? Difference between machine.config and Web.config?
    ASP.NET configuration files are XML-based text files--each named web.config--that can appear in any directory on an ASP.NET Web application server. Each web.config file applies configuration settings to the directory it is located in and to all virtual child directories beneath it. Settings in child directories can optionally override or modify settings specified in parent directories. The root configuration file--WinNT\Microsoft.NET\Framework\\config\machine.config—provides default configuration settings for the entire machine. ASP.NET configures IIS to prevent direct browser access to web.config
    files to ensure that their values cannot become public (attempts to access them will cause ASP.NET to return 403: Access Forbidden).
    At run time ASP.NET uses these web.config configuration files to hierarchically compute a unique collection of settings for each incoming URL target request (these settings are calculated only once and then cached across subsequent requests; ASP.NET automatically watches for file changes and will invalidate the cache if any of the configuration files change).

What is the use of sessionstate tag in the web.config file?
Configuring session state: Session state features can be configured via the section in a web.config file. To double the default timeout of 20 minutes, you can add the following to the web.config file of an application:

Dot Net Interview Questions - Part 8

1. Which ASP.NET configuration options are supported in the ASP.NET implementation on the shared web hosting platform?
   A: Many of the ASP.NET configuration options are not configurable at the site, application or subdirectory level on the shared hosting platform. Certain options can affect the security, performance and stability of the server and, therefore cannot be changed. The following settings are the only ones that can be changed in your site’s web.config file (s):
   browserCaps
   clientTarget
   pages
   customErrors
   globalization
   authorization
   authentication
   webControls
   webServices
2. Briefly describe the role of global.asax?
3. How can u debug your .net application?
4. How do u deploy your asp.net application?
5. Where do we store our connection string in asp.net application?
6. Various steps taken to optimize a web based application (caching, stored procedure etc.)
7. How does ASP.NET framework maps client side events to Server side events.
   
   
8. Security types in ASP/ASP.NET? Different Authentication modes?
9. How .Net has implemented security for web applications?
10. How to do Forms authentication in asp.net?
11. Explain authentication levels in .net ?
12. Explain autherization levels in .net ?
13. What is Role-Based security?
    A role is a named set of principals that have the same privileges with respect to security (such as a teller or a manager). A principal can be a member of one or more roles. Therefore, applications can use role membership to determine whether a principal is authorized to perform a requested action.
14. How will you do windows authentication and what is the namespace? If a user is logged under integrated windows authentication mode, but he is still not able to logon, what might be the possible cause for this? In ASP.Net application how do you find the name of the logged in person under windows authentication?
15. What are the different authentication modes in the .NET environment?

     ="Windows|Forms|Passport|None">

       ="name"

         loginUrl="url" 

         protection="All|None|Encryption|Validation"

         timeout="30" path="/" >

         requireSSL="true|false"

         slidingExpiration="true|false">

         ="Clear|SHA1|MD5">

            ="username" password="password"/>

       internal"/>

Attribute	Option	Description
Mode		Controls the default authentication mode for an application.
	Windows	Specifies Windows authentication as the default authentication mode. Use this mode when using any form of Microsoft Internet Information Services (IIS) authentication: Basic, Digest, Integrated Windows authentication (NTLM/Kerberos), or certificates.
	Forms	Specifies ASP.NET forms-based authentication as the default authentication mode.
	Passport	Specifies Microsoft Passport authentication as the default authentication mode.
	None	Specifies no authentication. Only anonymous users are expected or applications can handle events to provide their own authentication.

16. How do you specify whether your data should be passed as Query string and Forms (Mainly about POST and GET)
    Through attribute tag of form tag.
17. What is the other method, other than GET and POST, in ASP.NET?
18. What are validator? Name the Validation controls in asp.net? How do u disable them? Will the asp.net validators run in server side or client side? How do you do Client-side validation in .Net? How to disable validator control by client side JavaScript?
    A set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation ("EnableClientScript" property set to true/false) using client script.
    The following validation controls are available in asp.net:
    RequiredFieldValidator Control, CompareValidator Control, RangeValidator Control, RegularExpressionValidator Control, CustomValidator Control, ValidationSummary Control.
19. Which two properties are there on every validation control? ControlToValidate, ErrorMessage

How do you use css in asp.net?
Within the section of an HTML document that will use these styles, add a link to this external CSS style sheet that
follows this form:

MyStyles.css is the name of your external CSS style sheet.

Dot Net Interview Questions - Part 7

1. How do u implement locking concept for dataset?
   
   
2. Asp.net and asp – differences?

Code Render Block	Code Declaration Block
	Compiled
Request/Response	Event Driven
	Object Oriented - Constructors/Destructors, Inheritance, overloading..
	Exception Handling - Try, Catch, Finally
	Down-level Support
	Cultures
	User Controls
	In-built client side validation
Session - weren't transferable across servers	It can span across servers, It can survive server crashes, can work with browsers that don't support cookies
built on top of the window & IIS, it was always a separate entity & its functionality was limited.	its an integral part of OS under the .net framework. It shares many of the same objects that traditional applications would use, and all .net objects are available for asp.net's consumption.
	Garbage Collection
	Declare variable with datatype
	In built graphics support
	Cultures

3. How ASP and ASP.NET page works? Explain about asp.net page life cycle?
4. Order of events in an asp.net page? Control Execution Lifecycle?

Phase	What a control needs to do	Method or event to override
Initialize	Initialize settings needed during the lifetime of the incoming Web request.	Init event (OnInit method)
Load view state	At the end of this phase, the ViewState property of a control is automatically populated as described in Maintaining State in a Control. A control can override the default implementation of the LoadViewState method to customize state restoration.	LoadViewState method
Process postback data	Process incoming form data and update properties accordingly.	LoadPostData method (if IPostBackDataHandler is implemented)
Load	Perform actions common to all requests, such as setting up a database query. At this point, server controls in the tree are created and initialized, the state is restored, and form controls reflect client-side data.	Load event (OnLoad method)
Send postback change notifications	Raise change events in response to state changes between the current and previous postbacks.	RaisePostDataChangedEvent method (if IPostBackDataHandler is implemented)
Handle postback events	Handle the client-side event that caused the postback and raise appropriate events on the server.	RaisePostBackEvent method(if IPostBackEventHandler is implemented)
Prerender	Perform any updates before the output is rendered. Any changes made to the state of the control in the prerender phase can be saved, while changes made in the rendering phase are lost.	PreRender event (OnPreRender method)
Save state	The ViewState property of a control is automatically persisted to a string object after this stage. This string object is sent to the client and back as a hidden variable. For improving efficiency, a control can override the SaveViewState method to modify the ViewState property.	SaveViewState method
Render	Generate output to be rendered to the client.	Render method
Dispose	Perform any final cleanup before the control is torn down. References to expensive resources such as database connections must be released in this phase.	Dispose method
Unload	Perform any final cleanup before the control is torn down. Control authors generally perform cleanup in Dispose and do not handle this event.	UnLoad event (On UnLoad method)

Note To override an EventName event, override the OnEventName method (and call base.OnEventName)

5. What are server controls?
   ASP.NET server controls are components that run on the server and encapsulate user-interface and other related functionality. They are used in ASP.NET pages and in ASP.NET code-behind classes.
6. What is the difference between Web User Control and Web Custom Control?
   Custom Controls
   Web custom controls are compiled components that run on the server and that encapsulate user-interface and other related functionality into reusable packages. They can include all the design-time features of standard ASP.NET server controls, including full support for Visual Studio design features such as the Properties window, the visual designer, and the Toolbox.
   There are several ways that you can create Web custom controls:
• You can compile a control that combines the functionality of two or more existing controls. For example, if you need a control that encapsulates a button and a text box, you can create it by compiling the existing controls together.
• If an existing server control almost meets your requirements but lacks some required features, you can customize the control by deriving from it and overriding its properties, methods, and events.
• If none of the existing Web server controls (or their combinations) meet your requirements, you can create a custom control by deriving from one of the base control classes. These classes provide all the basic functionality of Web server controls, so you can focus on programming the features you need.

If none of the existing ASP.NET server controls meet the specific requirements of your applications, you can create either a Web user control or a Web custom control that encapsulates the functionality you need. The main difference between the two controls lies in ease of creation vs. ease of use at design time.
Web user controls are easy to make, but they can be less convenient to use in advanced scenarios. You develop Web user controls almost exactly the same way that you develop Web Forms pages. Like Web Forms, user controls can be created in the visual designer, they can be written with code separated from the HTML, and they can handle execution events. However, because Web user controls are compiled dynamically at run time they cannot be added to the Toolbox, and they are represented by a simple placeholder glyph when added to a page. This makes Web user controls harder to use if you are accustomed to full Visual Studio .NET design-time support, including the Properties window and Design view previews. Also, the only way to share the user control between applications is to put a separate copy in each application, which takes more maintenance if you make changes to the control.
Web custom controls are compiled code, which makes them easier to use but more difficult to create; Web custom controls must be authored in code. Once you have created the control, however, you can add it to the Toolbox and display it in a visual designer with full Properties window support and all the other design-time features of ASP.NET server controls. In addition, you can install a single copy of the Web custom control in the global assembly cache and share it between applications, which makes maintenance easier.

Web user controls	Web custom controls
Easier to create	Harder to create
Limited support for consumers who use a visual design tool	Full visual design tool support for consumers
A separate copy of the control is required in each application	Only a single copy of the control is required, in the global assembly cache
Cannot be added to the Toolbox in Visual Studio	Can be added to the Toolbox in Visual Studio
Good for static layout	Good for dynamic layout

7. Application and Session Events
   The ASP.NET page framework provides ways for you to work with events that can be raised when your application starts or stops or when an individual user's session starts or stops:
• Application events are raised for all requests to an application. For example, Application_BeginRequest is raised when any Web Forms page or XML Web service in your application is requested. This event allows you to initialize resources that will be used for each request to the application. A corresponding event, Application_EndRequest, provides you with an opportunity to close or otherwise dispose of resources used for the request.
• Session events are similar to application events (there is a Session_OnStart and a Session_OnEnd event), but are raised with each unique session within the application. A session begins when a user requests a page for the first time from your application and ends either when your application explicitly closes the session or when the session times out.

You can create handlers for these types of events in the Global.asax file.

8. Difference between ASP Session and ASP.NET Session?
   asp.net session supports cookie less session & it can span across multiple servers.
9. What is cookie less session? How it works?
   By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. If cookies are not available, a session can be tracked by adding a session identifier to the URL. This can be enabled by setting the following:
   
10. How you will handle session when deploying application in more than a server? Describe session handling in a webfarm, how does it work and what are the limits?
    By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. Additionally, ASP.NET can store session data in an external process, which can even reside on another machine. To enable this feature:
• Start the ASP.NET state service, either using the Services snap-in or by executing "net start aspnet_state" on the command line. The state service will by default listen on port 42424. To change the port, modify the registry key for the service: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\Port
• Set the mode attribute of the section to "StateServer".
• Configure the stateConnectionString attribute with the values of the machine on which you started aspnet_state.

The following sample assumes that the state service is running on the same machine as the Web server ("localhost") and uses the default port (42424):

Note that if you try the sample above with this setting, you can reset the Web server (enter iisreset on the command line) and the session state value will persist.

11. What method do you use to explicitly kill a users session?Abandon()
12. What are the different ways you would consider sending data across pages in ASP (i.e between 1.asp to 2.asp)?Session, public properties
13. What is State Management in .Net and how many ways are there to maintain a state in .Net? What is view state?
    Web pages are recreated each time the page is posted to the server. In traditional Web programming, this would ordinarily mean that all information associated with the page and the controls on the page would be lost with each round trip.
    To overcome this inherent limitation of traditional Web programming, the ASP.NET page framework includes various options to help you preserve changes — that is, for managing state. The page framework includes a facility called view state that automatically preserves property values of the page and all the controls on it between round trips.
    However, you will probably also have application-specific values that you want to preserve. To do so, you can use one of the state management options.
    Client-Based State Management Options:
    View State
    Hidden Form Fields
    Cookies
    Query Strings
    Server-Based State Management Options
    Application State
    Session State
    Database Support
14. What are the disadvantages of view state / what are the benefits?
    Automatic view-state management is a feature of server controls that enables them to repopulate their property values on a round trip (without you having to write any code). This feature does impact performance, however, since a server control's view state is passed to and from the server in a hidden form field. You should be aware of when view state helps you and when it hinders your page's performance.
15. When maintaining session through Sql server, what is the impact of Read and Write operation on Session objects? will performance degrade?
    Maintaining state using database technology is a common practice when storing user-specific information where the information store is large. Database storage is particularly useful for maintaining long-term state or state that must be preserved even if the server must be restarted.
16. What are the contents of cookie?
17. How do you create a permanent cookie?
18. What is ViewState? What does the "EnableViewState" property do?Why would I want it on or off?
19. Explain the differences between Server-side and Client-side code?
    Server side code will process at server side & it will send the result to client. Client side code (javascript) will execute only at client side.
20. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?

Dot Net Interview Questions - Part 6

1. What’s different about switch statements in C#?
   No fall-throughs allowed. Unlike the C++ switch statement, C# does not support an explicit fall through from one case label to another. If you want, you can use goto a switch-case, or goto default.
   case 1:
   cost += 25;
   break;
   case 2:
   cost += 25;
   goto case 1;
   
   
   
2. Advantage of ADO.Net?
• ADO.NET Does Not Depend On Continuously Live Connections
• Database Interactions Are Performed Using Data Commands
• Data Can Be Cached in Datasets
• Datasets Are Independent of Data Sources
• Data Is Persisted as XML
• Schemas Define Data Structures
3. How would u connect to database using .NET?
   SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated Security=SSPI;" + "Initial Catalog=northwind");
   nwindConn.Open();
4. What are relation objects in dataset and how & where to use them?
   In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table. Adding a DataRelation to a DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.
   The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains a column named CustID, which serves as a link between the two DataTable objects. The example adds a single DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child DataColumn.
   custDS.Relations.Add("CustOrders",
   custDS.Tables["Customers"].Columns["CustID"],
   custDS.Tables["Orders"].Columns["CustID"]);
   
   OR
   private void CreateRelation()
   {
   // Get the DataColumn objects from two DataTable objects in a DataSet.
   DataColumn parentCol;
   DataColumn childCol;
   // Code to get the DataSet not shown here.
   parentCol = DataSet1.Tables["Customers"].Columns["CustID"];
   childCol = DataSet1.Tables["Orders"].Columns["CustID"];
   // Create DataRelation.
   DataRelation relCustOrder;
   relCustOrder = new DataRelation("CustomersOrders", parentCol, childCol);
   // Add the relation to the DataSet.
   DataSet1.Relations.Add(relCustOrder);
   }

5. Difference between OLEDB Provider and SqlClient ?
Ans: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle provider, and faster than accessing database via the OleDb layer. It's faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.

6. What are the different namespaces used in the project to connect the database? What data providers available in .net to connect to database?
• System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.
• System.Data.SqlClient – classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
• System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.
• System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.
7. Difference between DataReader and DataAdapter / DataSet and DataAdapter?
   You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory.
   After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to retrieve rows from a data source, as shown in the following example.
   SqlDataReader myReader = myCommand.ExecuteReader();
   You use the Read method of the DataReader object to obtain a row from the results of the query.
   while (myReader.Read())
   Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
   myReader.Close();
   The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema definition language (XSD) schema.
   The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.
8. Which method do you invoke on the DataAdapter control to load your generated dataset with data? Fill()
9. Explain different methods and Properties of DataReader which you have used in your project?
   1. Read
   2. GetString
   3. GetInt32
   while (myReader.Read())
   Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
   myReader.Close();
10. What happens when we issue Dataset.ReadXml command?
    Reads XML schema and data into the DataSet.
11. In how many ways we can retrieve table records count? How to find the count of records in a dataset?
    foreach(DataTable thisTable in myDataSet.Tables){
    // For each row, print the values of each column.
    foreach(DataRow myRow in thisTable.Rows){
12. How to check if a datareader is closed or opened? IsClosed()
13. What happens when u try to update data in a dataset in .NET while the record is already deleted in SQL SERVER as backend?
    OR What is concurrency? How will you avoid concurrency when dealing with dataset? (One user deleted one row after that another user through his dataset was trying to update same row. What will happen? How will you avoid the problem?)
14. How do you merge 2 datasets into the third dataset in a simple manner? OR If you are executing these statements in commandObject. "Select * from Table1;Select * from Table2” how you will deal result set?
15. How do you sort a dataset?
16. If a dataset contains 100 rows, how to fetch rows between 5 and 15 only?
17. Differences between dataset.clone and dataset.copy?
    Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
    Copy - Copies both the structure and data for this DataSet.
18. What is the use of parameter object?
19. How to generate XML from a dataset and vice versa?
20. What is method to get XML and schema from Dataset?
    ans: getXML () and get Schema ()

Dot Net Interview Questions - Part 5

1. Can you explain what inheritance is and an example of when you might use it?
2. How can you write a class to restrict that only one object of this class can be created (Singleton class)?
3. What are the access-specifiers available in c#?
   Private, Protected, Public, Internal, Protected Internal.
4. Explain about Protected and protected internal, “internal” access-specifier?
   protected - Access is limited to the containing class or types derived from the containing class.
   internal - Access is limited to the current assembly.
   protected internal - Access is limited to the current assembly or types derived from the containing class.
5. Difference between type constructor and instance constructor? What is static constructor, when it will be fired? And what is its use?
   (Class constructor method is also known as type constructor or type initializer)
   Instance constructor is executed when a new instance of type is created and the class constructor is executed after the type is loaded and before any one of the type members is accessed. (It will get executed only 1st time, when we call any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention.
   A static constructor is used to initialize a class. It is called automatically to initialize the class before the first instance is created or any static members are referenced.
6. What is Private Constructor? and it’s use? Can you create instance of a class which has Private Constructor?
   A: When a class declares only private instance constructors, it is not possible for classes outside the program to derive from the class or to directly create instances of it. (Except Nested classes)
   Make a constructor private if:
   - You want it to be available only to the class itself. For example, you might have a special constructor used only in the implementation of your class' Clone method.
   - You do not want instances of your component to be created. For example, you may have a class containing nothing but Shared utility functions, and no instance data. Creating instances of the class would waste memory.
7. I have 3 overloaded constructors in my class. In order to avoid making instance of the class do I need to make all constructors to private?(yes)
8. Overloaded constructor will call default constructor internally?(no)
9. What are virtual destructors?
10. Destructor and finalize
    Generally in C++ the destructor is called when objects gets destroyed. And one can explicitly call the destructors in C++. And also the objects are destroyed in reverse order that they are created in. So in C++ you have control over the destructors.
    In C# you can never call them, the reason is one cannot destroy an object. So who has the control over the destructor (in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the objects only when necessary. Some situations of necessity are memory is exhausted or user explicitly calls System.GC.Collect() method.
    Points to remember:
    1. Destructors are invoked automatically, and cannot be invoked explicitly.
    2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
    3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may be declared in it.
    4. Destructors cannot be used with structs. They are only used with classes.
    5. An instance becomes eligible for destruction when it is no longer possible for any code to use the instance.
    6. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for destruction.
    7. When an instance is destructed, the destructors in its inheritance chain are called, in order, from most derived to least derived.
    
11. What is the difference between Finalize and Dispose (Garbage collection)
    Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object.
    In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object. Dispose can be called even if other references to the object are alive.
    Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to call Dispose.
12. What is close method? How its different from Finalize & Dispose?
13. What is boxing & unboxing?
14. What is check/uncheck?
15. What is the use of base keyword? Tell me a practical example for base keyword’s usage?
16. What are the different .net tools which u used in projects?
17. try
    {
    ...
    }
    catch
    {
    ...//exception occurred here. What'll happen?
    }
    finally
    {
    ..
    }
    Ans : It will throw exception.
18. What will do to avoid prior case?
    try

   {

    try

    {

      ...

    }

    catch

    {

     ...

     //exception occurred here.

    }

    finally

    {

     ...

    }

   }

   catch

   {

     ...

   }

   finally{...}

19.       try

     {

       ...

     }

     catch

     {

       ...

     }

     finally

     {

       ...

     } 

Will it go to finally block if there is no exception happened?
Ans: Yes. The finally block is useful for cleaning up any resources allocated in the try block. Control is always passed to the finally block regardless of how the try block exits.

20. Is goto statement supported in C#? How about Java?
    Gotos are supported in C#to the fullest. In Java goto is a reserved keyword that provides absolutely no functionality.