CSS rule to disable text selection highlighting

<style>

     * {
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: -moz-none;
    -o-user-select: none;
    user-select: none;
     }

</style>

Null coalescing operator

Null coalescing

x ?? y

Evaluates to y if x is null, to x otherwise

Dependency Injection

Dependency Injection (DI) is a software design pattern that allow us to develop loosely coupled code. DI is a great way to reduce tight coupling between software components. DI also enables us to better manage future changes and other complexity in our software. The purpose of DI is to make code maintainable.

The Dependency Injection pattern uses a builder object to initialize objects and provide the required dependencies to the object means it allows you to "inject" a dependency from outside the class. 


For example, Suppose your Client class needs to use a Service class component, then the best you can do is to make your Client class aware of an IService interface rather than a Service class. In this way, you can change the implementation of the Service class at any time (and for how many times you want) without breaking the host code.

 

We have following different ways to implement DI :

Constructor Injection

1. This is the most common DI.
2. Dependency Injection is done by supplying the DEPENDENCY through the class’s constructor when instantiating that class.
3. Injected component can be used anywhere within the class.
4. Should be used when the injected dependency is required for the class to function.
5. It addresses the most common scenario where a class requires one or more dependencies.

public interface IService
{
 void Serve();
}
 
public class Service : IService
{
 public void Serve()
 {
 Console.WriteLine("Service Called");
 //To Do: Some Stuff
 }
}
 
public class Client
{
 private IService _service;
 
 public Client(IService service)
 {
 this._service = service;
 }
 
 public void Start()
 {
 Console.WriteLine("Service Started");
 this._service.Serve();
 //To Do: Some Stuff
 }
}
class Program
{
 static void Main(string[] args)
 {
 client = new Client(new Service());
 client.Start();
 
 Console.ReadKey();
 }
}
 
 

The Injection happens in the constructor, by passing the Service that implements the IService-Interface. The dependencies are assembled by a "Builder" and Builder responsibilities are as follows:

1. knowing the types of each IService
2. according to the request, feed the abstract IService to the Client

Property injection

1. Also called Setter injection.
2. Used when a class has optional dependencies, or where the implementations may need to be swapped. Different logger implementations could be used this way.
3. May require checking for a provided implementation throughout the class(need to check for null before using it).
4. Does not require adding or modifying constructors.

public interface IService
{
 void Serve();
}
 
public class Service : IService
{
 public void Serve()
 {
 Console.WriteLine("Service Called");
 //To Do: Some Stuff
 }
}
 
public class Client
{
 private IService _service;
 
 public IService Service
 {
 set
 {
 this._service = value;
 }
 }
 
 public void Start()
 {
 Console.WriteLine("Service Started");
 this._service.Serve();
 //To Do: Some Stuff
 }
}
class Program
{
 static void Main(string[] args)
 {
 Client client = new Client();
 client.Service = new Service();
 client.Start();
 
 Console.ReadKey();
 }
}

Method injection

1. Inject the dependency into a single method, for use by that method.
2. Could be useful where the whole class does not need the dependency, just the one method.
3. Generally uncommon, usually used for edge cases.

public interface IService
{
 void Serve();
}
 
public class Service : IService
{
 public void Serve()
 {
 Console.WriteLine("Service Called");
 //To Do: Some Stuff
 }
}
 
public class Client
{
 private IService _service;
 
 public void Start(IService service)
 {
 this._service = service;
 Console.WriteLine("Service Started");
 this._service.Serve();
 //To Do: Some Stuff
 }
}
class Program
{
 static void Main(string[] args)
 {
 Client client = new Client();
 client.Start(new Service());
 
 Console.ReadKey();
 }
}
 
 

Key points about DI

1. Reduces class coupling
2. Increases code reusing
3. Improves code maintainability
4. Improves application testing

What's the difference between SQL Replication and SQL Database Mirror?

A.)

Mirroring:-

The Mirror database is not accessible for read or write access.

Replication:-

The Subscriber Database (backup site) is open to reads and writes.

B.)

Mirroring:-

Information flow will be only one way (from Principal to Mirror Server)

Replication:-

Changes can be merged, bi-directional changes can be made, so the information can flow from Publisher to Subscriber and the other way around.

C.)

Mirroring:-

In case of failure of the Principal Database, the Mirror Database will take over the control and will act as Principal and applications can be redirected automatically to connect to this new Principal Server. Very little downtime. No code change required in the application.

Replication:-

In case of failure on Publisher, applications need to be re-directed to the Subscriber manually (in case you really want to do that), requires code change in the app or the connection string.

D.)

Mirroring:-

Almost everything inside the DB is replicated to the DR site, Schema changes can be replicated easily.

Replication:-

You have the option to replicate selected set of tables/SP/functions inside the DB, Schema changes can give some hiccups.

In Short, Mirroring is a good tool for DR (Disaster Recovery) with very little downtime, but the drawback is that the DR site will *not* be accessible to users, whereas Replication can be used to Merge Data between two Servers, can act as a good tool for Reporting purposes as the backup site is accessible to the users, can also act a DR solution.

It all depends on what you need, what are the business requirements , which will help you to choose the right topology in your environment. You can go through SQL Books Online for more details about Mirroring and Replication.

Difference between Row_Number, Rank, Dense_Rank in Sql Server

Row_Number

Returns the sequential number of a row within a partition of a result set, starting at 1 for the first row in each partition.

ROW_NUMBER ( ) OVER ([<partition_by_clause>] <order_by_clause>)

Rank 
Returns the rank of each row within the partition of a result set.<br/> The rank of a row is one plus the number of ranks that come before the row in question.

RANK ( )    OVER ([< partition_by_clause >] < order_by_clause >)

Dense_Rank

 Returns the rank of rows within the partition of a result set,<br/> without any gaps in the ranking. The rank of a row is one plus the number of distinct ranks that come before the row in question.

DENSE_RANK ( )    OVER ([<partition_by_clause> ] < order_by_clause > )

NTILE 

Distributes the rows in an ordered partition into a specified number of groups. <br/>The groups are numbered, starting at one. For each row, NTILE returns the number of the group to which the row belongs.

NTILE (integer_expression) OVER ([<partition_by_clause>] < order_by_clause >)

Where

<partition_by_clause>

Divides the result set produced by the From clause into partitions to which the Row_Number/ Rank/ Dense_Rank/ Ntile function is applied.

<order_by_clause>

Determines the order in which the Row_Number/ Rank/ Dense_Rank/ Ntile values are applied to the rows in a partition.

We will apply these function on the below customer product table CustProd.

name	Product
cust1	decoder
cust2	cable
cust1	cable
cust2	package
cust3	decoder
cust3	cable

Please see the below snapshot for understanding of these function through example

With partition by product and order by name,

When we use partition by product, then it divides the result on the basis of product, as there are three distinct products then there will be 3 partitions.

After partition, order by name is used, that means, in the partitions Row Number, Rank or Dense Rank will be assigned as per the order of name. Here in the below result we see that rank ,row number and dense rank, all are having same value, It’s because in each partition there are distinct name given, if name would have been repeated for the same product then those records will have same rank and dense rank, but row number would have been same as shown below.

When used order by product instead of name, then we see in the below result that, the Rank and dense Rank were 1, Because we did partition of result by product , that means there will be common product in each partition , and rank and dense rank will also be same for same product.

ViewBag & ViewData :

Similarities between ViewBag & ViewData :

1. Helps to maintain data when you move from controller to view.
2. Used to pass data from controller to corresponding view.
3. Short life means value becomes null when redirection occurs. This is because their goal is to provide a way to communicate between controllers and views. It’s a communication mechanism within the server call.
4.  

Difference between ViewBag & ViewData:

1. ViewData is a dictionary of objects that is derived from ViewDataDictionary class and accessible using strings as keys.
2. ViewBag is a dynamic property that takes advantage of the new dynamic features in C# 4.0.
3. ViewData requires typecasting for complex data type and check for null values to avoid error.
4. ViewBag doesn’t require typecasting for complex data type.

CREATE WCF POST Restful service

CREATE WCF POST Restful service

Introduction


In my last article to explain about WCF Restful service using HTTP Get method.  This works well as long as you are sending small data as information to the service. But if want to deliver huge data, HTTP GET Method is not a good choice.  

When i write any WCF service, i always use POST. Reason is the advantage of POST over GET. Using HTTP POST method, you can almost achieve everything which you can achieve from GET. Despite of this you will get some additional feature if use POST. We might say that "GET" is basically for just getting (retrieving) data whereas "POST" may involve anything, like storing or updating data, or ordering a product, or sending E-mail etc. 

POST

1) Easy Character Encoding using application/x-www-form-urlencoded

2) No Proxy by default so always actual data from web server. 

3) Data length can be restricted by webserver, not by browser.

GET  

1) Character encoding will reduce the amount of data that can be used because of url encoding entities (i.e. three Japanese characters are converted to this: %26%2312454%3B%26%2312455%3B%26%2312502%3B)

2) Running a http request with GET can be cached on your web browser or a configured proxy server.

3) Maximum URL length is 2,083 characters in Internet Explorer (see MaxClientRequestBuffer: Use POST instead of GET to Send Large Amounts of Data in Request)

and lot more  

Extremely long URLs are usually a mistake. URLs over 2,000 characters will not work in the most popular web browser. Sending long information via URL is not a good way of implementation and also there has many restrictions i.e. max length of URL, Information format bla bla bla. For example Internet Explorer has a limitation implemented at 2083 characters. URIs is meant to be readable not to send information. 

So if you are writing any REST service and your information is long enough, better to choose POST instead of GET method.

In this article, i am going to create WCF Restful service using POST method and access it using HTTP Request. So we will have client and server both in this example code. I am creating one service which accepts HTTP Post XML request and response request data in XML format.  

STEP-1) 

Launch Visual Studio 2010. Click FILE->NEW->PROJECT. Create new "WCF Service Application". .

STEP-2) 

Once you create the project, you can see in solution that By Default WCF service and interface file are already created. Delete By default created file as we will create our own interface and WCF service file.

STEP-3)  

Now right click on solution and create one new WCF service file. I have given name to the service file as “RestServiceImpl.svc”.

STEP-4)  

We will create two DataContract classes for request and response purpose.

RequestData will receive the request from the client and ResponseData response. One very important thing is that POST XML format to the service should be same as RequestData. So the post xml request format can be like below:  

We must have to use namespace for the data contract in POST RESTFul service, which have multiple use i.e. reflects the current version of your code. The Same namespace should use in XML to Post data. Here i have given http://www.eysnap.com/mPlayer as namespace which can be changed.

STEP-5) 

Now we will write the OperationContract in IRestServiceImpl which is an interface.  Below is the code for that. 

As we can see in above code that here, Request and Response format is XML. We can change it to JSON also by changing the WebMessageFormat  from WebMessageFormat.Xml to WebMessageFormat.Json 

STEP-6 

Implementation of Auth OperationContract in RestServiceImpl.svc.cs here.

STEP-7)  

Now let’s move to configuration part which is the last one. There will be two basic parts of the configurations file which we must have to understand.

Services 

Behaviors 

And that’s it. Our Restful WCF POST RESTful service is ready to test. SERVICE IS READY I have created one Test WebClient in C# which makes Http request with some XML data. My application is hosted on localhost and URL is http://localhost:35798/RestServiceImpl.svc/auth . I launched and invoked service using WebClient. Below is my XML response which is correct one.