------------------------------------------------- // Interface
-------------------------------------------------
//
-------------------------------------------------
public interface IChoice
-------------------------------------------------
{
-------------------------------------------------
string Buy();
-------------------------------------------------
}
-------------------------------------------------
A new class will be added and this class we will be called factory class. This class sits between the client class and the business class and based on user choice it will return the respective class object through the interface. It will solve problem 3//
-------------------------------------------------
// Factory Class
-------------------------------------------------
//
-------------------------------------------------
public class FactoryChoice
-------------------------------------------------
{
-------------------------------------------------
static public IChoice getChoiceObj(string cChoice)
-------------------------------------------------
{
-------------------------------------------------
IChoice objChoice=null;
-------------------------------------------------
if (cChoice.ToLower() == "car") { objChoice = new clsCar(); }
-------------------------------------------------
else if (cChoice.ToLower() == "bike") { objChoice = new clsBike(); }
-------------------------------------------------
else { objChoice = new InvalidChoice();}
-------------------------------------------------
return objChoice;
-------------------------------------------------
}
-------------------------------------------------
}
-------------------------------------------------

------------------------------------------------- //Business classes
-------------------------------------------------
//Car
-------------------------------------------------
public class clsBike:IChoice
-------------------------------------------------
{
-------------------------------------------------
#region IChoice Members
-------------------------------------------------

------------------------------------------------- public string Buy()
-------------------------------------------------
{
-------------------------------------------------
return ("You choose Bike");
-------------------------------------------------
}
-------------------------------------------------

------------------------------------------------- #endregion
-------------------------------------------------
}
-------------------------------------------------

------------------------------------------------- //Bike
-------------------------------------------------
public class clsCar:IChoice
-------------------------------------------------
{
-------------------------------------------------
#region IChoice Members
-------------------------------------------------

------------------------------------------------- public string Buy()
-------------------------------------------------
{
-------------------------------------------------
return ("You choose Car");
-------------------------------------------------
}
-------------------------------------------------
#endregion
-------------------------------------------------
}
From the client class call the factory class object and it will return the interface object. Through the interface object we will call the respective method.
-------------------------------------------------
//Client class
-------------------------------------------------
IChoice objInvoice;
-------------------------------------------------
objInvoice = FactoryClass.FactoryChoice.getChoiceObj(txtChoice.Text.Trim());
-------------------------------------------------
MessageBox.Show(objInvoice.Buy());

sing System; namespace TestUnityInjection23
{
public class Program { static void Main(string[] args) { Customer customer1 = new Customer(new BasicLogger()); Customer customer2 = new Customer(new AdvancedLogger());

Console.ReadLine(); } }

public class Customer { public Customer(ILogger logger) { logger.WriteToLog("creating the customer"); } }

public interface ILogger { void WriteToLog(string text); }

public class BasicLogger : ILogger { public void WriteToLog(string text) { Console.WriteLine(text); } }

public class AdvancedLogger : ILogger { public void WriteToLog(string text) { Console.WriteLine("*** {0} ***", text); } }
}
[OperationContract] string GetData(int value);

public string GetData(int value)
{
return string.Format("You entered: {0}", value);
}

private void button1_Click(System.Object sender, System.EventArgs e)
{
ServiceReference1.Service1Client client = new ServiceReference1.Service1Client(); string returnString;

returnString = client.GetData(textBox1.Text); label1.Text = returnString;
}
------------------------------------------------- public static class MyMathExtension
-------------------------------------------------
{ Public static int Subtract(this Maths x) { return x.Number1 - x.Number2;
-------------------------------------------------
}
}

Why do we want to have class as Abstract? Abstract – Abstract classes are incomplete classes, i.e., they will have combination of implemented and unimplemented methods along with data members, properties, events, delegates and indexers. The main idea to have class as abstract is to have only Base class that can be derivable and that will have basic functionality. As I mentioned above, we can have unimplemented method in abstract class that gives flexibility to derived classes to implement as required along with basic functionality. And also, we can’t instantiate object of abstract class. Abstract class can be with/without abstract methods. But if methods are declared as abstract in a class, that class also should be declared as abstract. | Access modifiers They support the concept of encapsulation, which promotes the idea of hiding functionality. publicThe type or member can be accessed by any other code in the same assembly or another assembly that references it.privateThe type or member can be accessed only by code in the same class or struct. protected The type or member can be accessed only by code in the same class or struct, or in a class that is derived from that class.internalThe type or member can be accessed by any code in the same assembly, but not from another assembly.protected internalProtected Internal variables/methods are accessible within the same assembly and also from the classes that are derived from this parent class..ASP.NET Page Life CyclePage request, Start, Initialization, Load, Postback event handling, Rendering, UnloadPage Life Cycle EventsPreInit, Init, InitComplete, PreLoad, Load, Control events, LoadComplete, PreRender, PreRenderComplete, SaveStateComplete, Render, Unload | What’s the difference between an interface and abstract class?Interfaces have all the methods having only declaration but no definition. In an abstract class, we can have some concrete methods. In an interface class, all the methods are public. An abstract class may have private methods. | | What is the difference between a Struct and a Class?Structs are value-type variables and classes are reference types. Structs stored on the stack, causes additional overhead but faster retrieval. Structs cannot be inherited. | | What is the difference between Finalize() and Dispose() methods?Dispose() is called when we want for an object to release any unmanaged resources with them. On the other hand Finalize() is used for the same purpose but it doesn’t assure the garbage collection of an object. | | What are generics in C#.NET?Generics are used to make reusable code classes to decrease the code redundancy, increase type safety and performance. Using generics, we can create collection classes. To create generic collection, System.Collections.Generic namespace should be used instead of classes such as ArrayList in the System.Collections namespace. Generics promotes the usage of parameterized types. | System.String and StringBuilder classes?System.String is immutable. When we modify the value of a string variable then a new memory is allocated to the new value and the previous memory allocation released. System.StringBuilder was designed to have concept of a mutable string where a variety of operations can be performed without allocation separate memory location for the modified string. | What is the difference between method overriding and method overloading?In method overriding, we change the method definition in the derived class that changes the method behavior. Method overloading is creating a method with the same name within the same class having different signatures. (using different types, different order, and different number of parameters.) | | What are the different ways a method can be overloaded?Methods can be overloaded using different data types for parameter, different order of parameters, and different number of parameters. | What are value types and reference types? Value types are stored in the Stack whereas reference types stored on heap.
Value types: int, enum , byte, decimal, double, float, longReference Types: string , class, interface, object. | Why can’t you specify the accessibility modifier for methods inside the interface?In an interface, we have virtual methods that do not have method definition. All the methods are there to be overridden in the derived class. That’s why they all are public. | What is the difference between public, static and void?All these are access modifiers in C#. Public declared variables or methods are accessible anywhere in the application. Static declared variables or methods are globally accessible without creating an instance of the class. The compiler stores the address of the method as the entry point and uses this information to begin execution before any objects are created. And Void is a type modifier that states that the method or variable does not return any value. | What is boxing?Boxing is the process of explicitly converting a value type into a corresponding reference type. Basically, this involves creating a new object on the heap and placing the value there. Reversing the process is just as easy with unboxing, which converts the value in an object reference on the heap into a corresponding value type on the stack. The unboxing process begins by verifying that the recipient value type is equivalent to the boxed type. If the operation is permitted, the value is copied to the stack. | What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods. | ref & out parameters?An argument passed as ref must be initialized before passing to the method whereas out parameter needs not to be initialized before passing to a method | What’s 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. | What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true. | What is an object pool in .NET?An object pool is a container having objects ready to be used. It tracks the object that is currently in use, total number of objects in the pool. This reduces the overhead of creating and re-creating objects. | Can we add variables and properties in interfaces in C#.NET?Variables in Interfaces - NO. Can you elaborate on why you need them? You can have variables in Base classes though.
Properties in Interfaces - Yes, since they are paired methods under the hood.
Members of an interface are implicitly public. You cannot specify access modifiers explicitly | System.String and System.Text.StringBuilder classes?System.String is immutable. When we modify the value of a string variable then a new memory is allocated to the new value and the previous memory allocation released. System.StringBuilder was designed to have concept of a mutable string where a variety of operations can be performed without allocation separate memory location for the modified string. | Webservice and WCFWCF provides a runtime environment for services, enabling you to expose CLR types as services, and to consume other services as CLR types.1. WCF has been designed by Microsoft from the scratch to comply with SOA (Service Oriented Architecutre). while Webservices do not comply with the Service Oriented Architecutre. 2. Webservice can only be hosted on IIS while WCF can be hosted on any server like WAS (Windows Activation Service), Self-hosting, Managed Windows Service. 3. WCF can be accessed via various protocols like SOAP over HTTP, Binary over TCP, Named Pipes, P2P, MSMQ etc. while webservices can only be accessed via HTTP. 4. [WebService] attribute has to be added to the class and [WebMethod] attribute to be added to the method exposed to client in case of webservice while [ServiceContraact] attribute is added to the class and [OperationContract] attribute is added to the method exposed to client in case of WCF. 5. System.Xml.Serialization namespace is used for serialization in webservice while System.Runtime.Serialization namespace is used for serialization in case of WCF. 6. WCF can be multithreaded via ServiceBehavior class while webservices cannot be multithreaded. | View state: the good, badView State provides us with a beautiful mechanism to implement state management of server controls and web forms in .Net. The remarkable option to persist the state with the client machine during round trips to and from the server without using server memory or cache and cookies is a very powerful capability offered to the developer. The Bad:All this sounds very nice. But coming back to the reality of things, there are a couple of limitations that a seasoned programmer will have to keep in mind in order to have an efficient, performance driven application running. Taking a look at some of these points, the drawbacks of working with viewstate will become lucid.1. Overhead charges: First of all, the hidden input field that we hold inside our generated web page becomes an overhead. Although no server resources, caching or cookies are used by the view state, it does add a few kilo bytes to the webpage. Therefore, with this extra weight, loading time for the webpage in the client machine does get affected. Such miniscule numbers can actually make a noticeable performance issue if we are talking about web pages going through lot of hits and playing around with lots of other controls.2. Insecure data: The possibility of having plain text passed to the client during round trips can aid in malicious intent. Therefore it becomes a best practice NOT to store important information in our view state. | What is endpoint in WCF?Every service must have Address that defines where the service resides, Contract that defines what the service does and a Binding that defines how to communicate with the service. In WCF the relationship between Address, Contract and Binding is called Endpoint. The Endpoint is the fusion of Address, Contract and Binding. | What are contracts in WCF?In WCF, all services expose contracts. The contract is a platform-neutral and standard way of describing what the service does. | How to define a REST based service in WCF?By adding the WebGetAttribute, we can define a service as REST based service that can be accessible using HTTP GET operation.WCF 3.5 provides explicit support for RESTful communication using a new binding named WebHttpBinding. [ServiceContract(Namespace = "http://url. Samples")]interface IStock{[OperationContract][WebGet]int GetStock(string StockId);}What Message Exchange Patterns (MEPs) supported by WCF? Explain each of them briefly.1. Request/Response 2. One Way 3. DuplexRequest/ResponseIt’s the default pattern. In this pattern, a response message will always be generated to consumer when the operation is called, even with the void return type. In this scenario, response will have empty SOAP body.One WayIn some cases, we are interested to send a message to service in order to execute certain business functionality but not interested in receiving anything back. OneWay MEP will work in such scenarios. If we want queued message delivery, OneWay is the only available option.DuplexThe Duplex MEP is basically a two-way message channel. In some cases, we want to send a message to service to initiate some longer-running processing and require a notification back from service in order to confirm that the requested process has been completed. | WCF defines four types of contracts. Service contracts Describe which operations the client can perform on the service. There are two types of Service Contracts. ServiceContract - This attribute is used to define the Interface. OperationContract - This attribute is used to define the method inside Interface. Data contracts Define which data types are passed to and from the service. WCF defines implicit contracts for built-in types such as int and string, but we can easily define explicit opt-in data contracts for custom types. There are two types of Data Contracts. DataContract - attribute used to define the class DataMember - attribute used to define the properties. [DataContract]class Contact{ [DataMember] public string FirstName; [DataMember] public string LastName;}If DataMember attributes are not specified for a properties in the class, that property can't be passed to-from web service. Fault contracts Define which errors are raised by the service, and how the service handles and propagates errors to its clients. Message contracts Allow the service to interact directly with messages. Message contracts can be typed or untyped, and are useful in interoperability cases and when there is an existing message format we have to comply with. | | | What are page directives?The first line of an ASP.NET page is the page directive; you will find it on all ASP.NET pages. These directives are instructions for the page. It begins with the @Page directive and continues with the various attributes available to this directive.It's unreasonable to expect a candidate to know all of these attributes, but a few popular ones include the following. * AutoEventWireup: Indicates whether page events are autowired. * CodeBehind: The name of the compiled class associated with the page. * Debug: Indicates whether the page is compiled in debug mode (includes debug symbols). * EnableTheming: Indicates whether themes are used on the page. * EnableViewState: Indicates whether view state is maintained across pages. * ErrorPage: Specifies a target URL to be used when unhandled exceptions occur. * Language: Indicates the language used when compiling inline code on the page. * Trace: Signals whether tracing is enabled on the page. | How can you pass values between ASP.NET pages?There are numerous ways to accomplish this task; the option you choose depends on the environment. The oldest way to approach it is via the QueryString (i.e., passing values via URL); this is also one of the least secure ways because users can easily see the data and could possibly hack the site/page by changing parameter values. Next, you can use HTTP POST to pass values; these are available via a collection within the ASP.NET page. More specific to ASP.NET is the use of Session state, which makes information available to all pages within the ASP.NET application. Another approach is using public properties on the source page and accessing these properties on the target page. Also, you can use the PreviousPage property of the current page to access control information on the referring page. The last two require the source, and target pages are within the same ASP.NET application. | What is the global.asax file?The global.asax file is an optional piece of an ASP.NET application. It is located in the root of the application directory structure. It cannot be directly loaded or requested by users. It provides a place to define application- and session-wide events. You can define your own events, but it does contain default Application events like when the application starts Application_Start and ends with Application_End. The same is true for Session events (Session_Start and Session_End). | How does PostBack work?PostBack is basically the ASP.NET submitting a form to it -- it posts back to the current URL. The JavaScript __doPostBack function is placed on the page (look at the source within the browser) to facilitate. PostBack uses ViewState to remember controls and data. The IsPostBack property of the ASP.NET page allows you to determine if the loading of the page is the result of a postback event; this is done in the Page_Load event. | How can you loop through all controls on an ASP.NET Web form?You can easily traverse all controls on a form via the Web Form's Controls collection. The GetType method can be used on each control to determine its type and how to work with it. Now, it gets tricky because the form contains a tree of controls; that is, some controls are contained within others (think of a Table). You would have to recursively loop through the controls to make sure everything is processed. | What are C# attributes and its significance?C# provides developers a way to define declarative tags on certain entities eg. Class, method etc. are called attributes. The attribute’s information can be retrieved at runtime using Reflection | | | | | | | | |

Difference between truncate and delete?Truncate is a quick way to empty a table. It removes everything without logging each row. Truncate will fail if there are foreign key relationships on the table. Conversely, the delete command removes rows from a table, while logging each deletion and triggering any delete triggers that may be present | Advantages of using Stored Procedures?Stored procedure can reduced network traffic and latency, boosting application performance.Stored procedure execution plans can be reused, staying cached in SQL Server's memory, reducing server overhead.Stored procedures help promote code reuse.Stored procedures can encapsulate logic. You can change stored procedure code without affecting clients.Stored procedures provide better security to your data. | What are DMVs?Dynamic management views (DMVs) and functions return server state information that can be used to monitor the health of a server instance, diagnose problems, and tune performance; that is, they let you see what is going on inside SQL Server. They were introduced in SQL Server 2005 as an alternative to system tables. One example is viewing operating system wait statistics via this query. | What are temp tables? What is the difference between global and local temp tables?Temporary tables are temporary storage structures. You may use temporary tables as buckets to store data that you will manipulate before arriving at a final format. The hash (#) character is used to declare a temporary table as it is prepended to the table name. A single hash (#) specifies a local temporary table. | Joins 1. Inner join: is a join which returns only the rows for which there is an equal value in the join column. Inner joins can be specified in either the FROM or WHERE caluses. 2. Outer join: is a join which returns all the rows from the at least one of the tables mentioned in the FROM clause and meeting the condition in the WHERE clause. Outer joins can be specified in the FROM clause only.All rows are retrieved from the left table referenced with a left outer join and all rows retrieved from the right table with a right outer join.All rows from the both tables are returned in a full outer join. 3. Cross join: A cross join is join which does not have a WHERE clause and produces the cartesian product of the tables involved in the join.The size of the cartesian product result set is the number of rows in the first table multiplied by the number of rows in the second table. 4. Self-Joins: A table can be joined to itself in a self-join. For example, you can use a self-join to find the products that are supplied by more than one vendor. | @table variable table variable is similar to temporary table except with more flexibility. It is not physically stored in the hard disk, it is stored in the memory. We should choose this when we need to store less 100 records. ------------------------------------------------- DECLARE @myTable TABLE (
AutoID int,myName char(50) )How do you optimize stored procedures in SQL Server 2005
1. Use as much as possible WHERE clause filters. Where Clause is the most important part for optimization
2. Select only those fields which really require.
3. Joins are expensive in terms of time. Make sure that use all the keys that relate the two tables together and don't join to unused tables, always try to join on indexed fields. The join type is important as well (INNER, OUTER). | What is the difference between a clustered and a nonclustered index?A clustered index affects the way the rows of data in a table are stored on disk. When a clustered index is used, rows are stored in sequential order according to the index column value; for this reason, a table can contain only one clustered index, which is usually used on the primary index value.A nonclustered index does not affect the way data is physically stored; it creates a new object for the index and stores the column(s) designated for indexing with a pointer back to the row containing the indexed values.You can think of a clustered index as a dictionary in alphabetical order, and a nonclustered index as a book's index. | What does the NOLOCK query hint do?Table hints allow you to override the default behavior of the query optimizer for statements. They are specified in the FROM clause of the statement. While overriding the query optimizer is not always suggested, it can be useful when many users or processes are touching data. The NOLOCK query hint is a good example because it allows you to read data regardless of who else is working with the data; that is, it allows a dirty read of data -- you read data no matter if other users are manipulating it. A hint like NOLOCK increases concurrency with large data stores. | What is a query execution plan?SQL Server has an optimizer that usually does a great job of optimizing code for the most effective execution. A query execution plan is the breakdown of how the optimizer will run (or ran) a query. There are several ways to view a query execution plan. This includes using the Show Execution Plan option within Query Analyzer; Display Estimated Execution Plan on the query dropdown menu; or use the SET SHOWPLAN_TEXT ON command before running a query and capturing the execution plan event in a SQL Server Profiler trace. | What is trigger?Triggers allows us to execute a batch of SQL code when either an insert, update or delete command is executed against a specific table.
Triggers are special types of stored procedures that are defined to execute automatically in place of or after data modifications. They can be executed automatically on the insert, delete and update operation.1. Insert 2. Delete 3. Update 4. Instead of | Implict Transaction And Explict TransactionImplicit Transaction is the auto commit. There is no beginning or ending of the transaction.

Explicit Transaction has the beginning, ending and rollback of transactions with the command Begin Transaction
Commit Transaction and Rollback Transation
In the explicit transaction, if an error occurs in between we can rollback to the begining of the transaction which cannot be done in implicit transaction. | HAVING CLAUSE and a WHERE CLAUSE?You can use Having Clause with the GROUP BY function in query and WHERE Clause is applied to each row before they are part of the GROUP BY function in a query. | Varchar and char: varchar are variable length strings with a maximum length specified. If a string is less than the maximum length, then it is stored verbatim without any extra characters. char are fixed length strings with a set length specified. If a string is less than the set length, then it is padded with extra characters so that it's length is the set length.
Use varchar when your strings do not have a fixed length (e.g. names, cities, etc.)
Use char when your strings are always going to be the same length (e.g. phone numbers, zip codes, etc). | What is log shipping? Logshipping is a new feature of SQL Server 2000. We should have two SQL Server - Enterprise Editions. From Enterprise Manager we can configure the logshipping. In logshipping the transactional log file from one server is automatically updated into the backup database on the other server. If one server fails, the other server will have the same db and we can use this as the DR (disaster recovery) plan. | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

What is WCF?

Windows Communication Foundation (WCF) is an SDK for developing and deploying services on Windows. WCF provides a runtime environment for services, enabling you to expose CLR types as services, and to consume other services as CLR types.

What is service and client in perspective of data communication?

WCF supports following transport schemas

HTTP
TCP
Peer network
IPC (Inter-Process Communication over named pipes)
MSMQ

The sample address for above transport schema may look like

http://localhost:81 http://localhost:81/MyService net.tcp://localhost:82/MyService net.pipe://localhost/MyPipeService net.msmq://localhost/private/MyMsMqService
net.msmq://localhost/MyMsMqService