Dot Net Programming

 Ref and out keywords in c# are used to pass arguments within a method or function. Both indicate that an argument passed by reference. By default parameter are passed to a method by value. By using these keywords we can pass a parameter by reference.

Ref –

The ref keyword is used to pass an argument as a reference. This means that value of that parameter is changed in method, it get reflected in calling method.

 public static string GetNextName(ref int id)  

  {  

    string returnText = "Next-" + id.ToString();  

    id += 1;  

    return returnText;  

  }  

 static void Main(string[] args)  

  {  

    int val = 1;  

    Console.WriteLine("Previous value of integer val:" + val.ToString());  

    string test = GetNextName(ref val);  

    Console.WriteLine("Current value of integer val:" + val.ToString());  

  } 

Out –

The out keyword is used to pass arguments to method as a reference type and is primary used when a method has to return multiple values.

 public static string GetNextNameByOut(out int id)  

  {  

    id = 1;  

    string returnText = "Next-" + id.ToString();  

    return returnText;   

  }  

 static void Main(string[] args)  

  {  

    int val = 0;  

    Console.WriteLine("Previous value of integer val:" + val.ToString());  

    string test = GetNextNameByOut(out val);  

    Console.WriteLine("Current value of integer val:" + val.ToString());  

  } 

 Global.asax file is derived from the HttpApplication class and contains code for responding to application-level events raised by ASP.NET. Global.asax file, also known as ASP.NET application file, is located in root directory of an ASP.NET application.

Note 1 : The Global.asax is an optional file. Use it only when there is a need for it.

Note 2 : If a user requests the Global.asax file, the request is rejected . External users can not use it.

The following are some of the important events in the Global.asax file:

Application_Init : The Application_Init event is fired when an application initializes the first time.

Application_Start  : The Application_Start event is fired the first time when an application starts.

Application_AutorizeRequest : Application_AutorizeRequest event is  fired on successful authentication of users credentials. You can use this method to authorization rights to user.

Application_ResolveRequestCache : Application_ResolveRequestCache is fired on successful completion of an authorization request.

Application_Disposed : Application_Disposed  event is fired when the web application is destroyed.

Session_Start : Session_Start event is fired when session starts on each new user requesting a page.

Application_BeginRequest :  The Application_BeginRequest event is fired when each time new user request come in.

Application_EndRequest : The Application_EndRequest event is fired at the end of each request.

Application_AuthenticateRequest : The Application_AuthenticateRequest event indicates that a request is ready to be  authenticated. If you are using forms Authentication, this event can be used to check for the user’s roles & rights.

Application_Error : The Application_Error event fired when an error occurs.

Session_End : The Session_End event is fired when the session of a user ends.

Application_End : The Application_End event is fired when the web application ends.

In LINQ, Partition Operators are used for separating the given sequence into two portions without

Sorting the element and return the one of the portions

IList<string> strList = new List<string>(){ "One", "Two", "Three" };

var newList = strList.Take(2);

foreach(var str in newList)

    Console.WriteLine(str);

IList<string> strList = new List<string>() { 

                                            "Three", 

                                            "Four", 

                                            "Five", 

                                            "Hundred"  };

var result = strList.TakeWhile(s => s.Length > 4);

foreach(string str in result)

        Console.WriteLine(str);

In LINQ, Partition Operators are used for separating the given sequence into two portions without

Sorting the element and return the one of the portions

IList<string> strList = new List<string>() { 

                                            "One", 

                                            "Two", 

                                            "Three", 

                                            "Four", 

                                            "Five", 

                                            "Six"  };

var resultList = strList.SkipWhile(s => s.Length < 4);

foreach(string str in resultList)

        Console.WriteLine(str);

 LINQ queries are always executed when the query variable is iterated over, not when the query variable is created. This is called deferred execution. You can also force a query to execute immediately, which is useful for caching query results.

There are two type of linq query execution are given below:

Deferred query execution

DataContext objcontext = new DataContext();
var query = from customer in objcontext.Customers
 where customer.City == "Pune"
 select customer; // Query does not execute 

 foreach (var Customer in query) // Query executes 
 {
 Console.WriteLine(Customer.Name);
 }

Deferred execution provides the facility of query reusability since it always fetches the uploaded data from the data source which exists at the time of each execution.

Immediate Query Execution

DataContext objcontext = new DataContext();
var query = (from customer in objcontext .Customers
 where customer.City == "Pune"
 select customer).Count(); // Query execute