Expert Dot Net

In ASP.NET MVC, controllers define action methods and these action methods generally have a one-to-one relationship with UI controls, such as clicking a button or a link, etc. For example, in one of our previous examples, the UserController class contained methods UserAdd, UserDelete, etc.

However, many times we would like to perform some action before or after a particular operation. For achieving this functionality, ASP.NET MVC provides a feature to add pre- and post-action behaviors on the controller's action methods.

Types of Filters

ASP.NET MVC framework supports the following action filters −

1. Action Filters − Action filters are used to implement logic that gets executed before and after a controller action executes. We will look at Action Filters in detail in this chapter.
2. Authorization Filters − Authorization filters are used to implement authentication and authorization for controller actions.
3. Result Filters − Result filters contain logic that is executed before and after a view result is executed. For example, you might want to modify a view result right before the view is rendered to the browser.
4. Exception Filters − Exception filters are the last type of filter to run. You can use an exception filter to handle errors raised by either your controller actions or controller action results. You also can use exception filters to log errors.

Action filters are one of the most commonly used filters to perform additional data processing, or manipulating the return values or cancelling the execution of action or modifying the view structure at run time.

Action Filters

Action Filters are additional attributes that can be applied to either a controller section or the entire controller to modify the way in which an action is executed. These attributes are special .NET classes derived from System.Attribute which can be attached to classes, methods, properties, and fields.

ASP.NET MVC provides the following action filters −

1. Output Cache − This action filter caches the output of a controller action for a specified amount of time.
2. Handle Error − This action filter handles errors raised when a controller action executes.
3. Authorize − This action filter enables you to restrict access to a particular user or role.

Now, we will see the code example to apply these filters on an example controller ActionFilterDemoController. (ActionFilterDemoController is just used as an example. You can use these filters on any of your controllers.)

Output Cache

Example − Specifies the return value to be cached for 10 seconds.

Loop is used in programming when you need to repeat any group of statement or statement more then one time. For loop is one important looping construct which is used to iterate set of instructions.

for ( int i=0 ; i <= 5 ; i++)

{

// Your statements

}

There are 4 parts of this for loop.

- First part is initialization

- Second part is condition checking

- Third part is increment / decrements

- Fourth part is group of statements which basically would be executed.

Demo 1 :

Introduction to WCF

Windows Communication Foundation (Code named Indigo) is a programming platform and runtime system for building, configuring and deploying network-distributed services. It is the latest service oriented technology; Interoperability is the fundamental characteristics of WCF. It is unified programming model provided in .Net Framework 3.0. WCF is a combined features of Web Service, Remoting, MSMQ and COM+. WCF provides a common platform for all .NET communication.

Please refer the below Image

There are certain advantages and disadvantages as well which is given below :

Advantage

WCF is interoperable with other services when compared to .Net Remoting,where the client and service have to be .Net.

WCF services provide better reliability and security in compared to ASMX web services.

In WCF, there is no need to make much change in code for implementing the security model and changing the binding. Small changes in the configuration will make your requirements.

WCF has integrated logging mechanism, changing the configuration file settings will provide this functionality. In other technology developer has to write the code.

Disadvantage

Making right design for your requirement is little bit difficult. I will try to help you on solving these difficulties in the following article.

C#-Basic Syntax 

C# is an object-oriented programming language. In Object-Oriented Programming methodology, a program consists of various objects that interact with each other by means of actions. The actions that an object may take are called methods. Objects of the same kind are said to have the same type or, are said to be in the same class.

For example, let us consider a Rectangle object. It has attributes such as length and width. Depending upon the design, it may need ways for accepting the values of these attributes, calculating the area, and displaying details.

Let us look at demo of a Rectangle class and discuss C# basic syntax:

using System;

namespace RectangleDemo

{

   class Rectangle 

   {

      // member variables

      double length;

      double width;

      public void Acceptdetails()

      {

         length = 4.5;    

         width = 3.5;

      }

      public double GetArea()

      {

         return length * width; 

      }

      public void Display()

      {

         Console.WriteLine("Length: {0}", length);

         Console.WriteLine("Width: {0}", width);

         Console.WriteLine("Area: {0}", GetArea());

      }

   }

   class ExecuteRectangle 

   {

      static void Main(string[] args) 

      {

         Rectangle r = new Rectangle();

         r.Acceptdetails();

         r.Display();

         Console.ReadLine(); 

      }

   }

}

When the above code is compiled and executed, it produces the following result:

Length: 4.5

Width: 3.5

Area: 15.75

The using Keyword

The first statement in any C# program is

using System;

The using keyword is used for including the namespaces in the program. A program can include multiple using statements.

The class Keyword

The class keyword is used for declaring a class.

Comments in C#

Comments are used for explaining code. Compilers ignore the comment entries. The multiline comments in C# programs start with /* and terminates with the characters */ as shown below:

/* This program demonstrates

The basic syntax of C# programming 

Language */

Single-line comments are indicated by the '//' symbol. For example,

}//end class Rectangle    

Member Variables

Variables are attributes or data members of a class, used for storing data. In the preceding program, the Rectangle class has two member variables named length and width.

Member Functions

Functions are set of statements that perform a specific task. The member functions of a class are declared within the class. Our sample class Rectangle contains three member functions: AcceptDetails, GetArea and Display.

Instantiating a Class

In the preceding program, the class ExecuteRectangle contains the Main()method and instantiates the Rectangle class.

Identifiers

An identifier is a name used to identify a class, variable, function, or any other user-defined item. The basic rules for naming classes in C# are as follows:

·        A name must begin with a letter that could be followed by a sequence of letters, digits (0 - 9) or underscore. The first character in an identifier cannot be a digit.

·        It must not contain any embedded space or symbol such as? - + ! @ # % ^ & * ( ) [ ] { } . ; : " ' / and \. However, an underscore ( _ ) can be used.

·        It should not be a C# keyword.