DEV Community: Technology Crowds

How to parse HTML table using HTML Agility Pack C# |

Technology Crowds — Thu, 06 Aug 2020 10:36:44 +0000

In this video demonstrated, how to parse HTML table using HTML Agility Pack. This tool is quite helpful to extract data from web and data scraping, data mining etc. Here is also used LINQ to extract data from HTML table as below:

1) Declare htmlweb and load html document using html agility-pack
2) Extracting HTML table from Web Page.
3) Finally show output

Learn Inheritance in C# programming with examples

Technology Crowds — Thu, 06 Aug 2020 09:37:40 +0000

Among the prominent overriding members, Inheritance is the most valuable member to create a new class that re-utilizes, expands, and updates the performance that is defined in some other class.

Base class and Derived class

Throughout inheritance, mainly two types of classes are used such as Base class and derived class. Generally, the class whose members get inherited is known as the base class, and the class, which inherits those members, is known as the derived class. On the other hand, whole classes in C# completely inherit from the Object class, which supports .NET class hierarchy and offers low-level services to whole classes.

But, C# never supports multiple inheritances and hence, only one base class will be specified for one derived class.

Codes to inherit from a base class:

Usually, all classes can be inherited as per the OOPS concept of C#. However, you have the option to specify whether a class should be used as a base class, or not. It all depends upon you to decide about creating a base class.

Find the following Codes to specify that a class cannot be used as a base class:

1 public sealed class A { }

Following codes are used to denote that a class can be used as a base class only and also, cannot be instantiated:

1 public abstract class B { }

Overriding Members

Generally, a derived class inherits all required members from the specific base class. If you wish to alter the actions of the inherited member, you have to override it definitely with some overriding members. Also, you can define a new execution of the method, event, or property in the present derived class.
The following C# modifiers are used in overriding the properties and methods.

C# Modifier and Definition

Virtual - It allows a specific class member to be overridden within a derived class.
Override - This modifier overrides a virtual or override able member that is defined within the base class.
Abstract - Describes that a class member can be overridden within the derived class by inheriting the class member from the base class.
Sealed - Specifies about non-use of class as a base class
New Modifier - Hides a particular member that is inherited from a base class as per requirement.

What are Interfaces?

Interfaces are similar to classes, which define a set of methods, properties, and events. But unlike classes, interfaces disallow implementation directly. They’re implemented through classes and defined as detach entities from classes. An interface stands for a contract in that a class, which implements an interface, needs to implement each aspect of the same interface accurately as it is defined.

Codes to define an interface:
1 interface ITCInterface
2 {
3 void DoSomething();
4 }

Codes to implement an interface within a class:
1 class SampleClass : ITCInterface
2 {
3 void ITCInterface.DoSomething()
4 {
5 // implementation method.
6 }
7 }

Hope the readers have thorough knowledge about the use of code for Inheritance, Overriding members and interfaces.

Learn use of Delegates in C# programming

Technology Crowds — Mon, 27 Jul 2020 16:46:11 +0000

Hope you must have gone through my previous articles Class members, Inheritance & Interface, and Generics. Now, we’ll discuss on Delegates. A delegate defines a signature method and can create a reference to any method with a well-matched signature. You can call the method only through the delegate. Delegates help pass methods as point a of view to other methods for the purpose of signature validation between two methods.

Please note that Event handlers are similar to methods that are called through delegates. The Event handling task is very much important for a programming aspect. Hence, delegates are broadly used in event handling.

Codes to create a delegate:
1 public delegate void TCDelegate(string str);

Codes to create a reference to a method, which perfectly matches the signature mentioned by the delegate:

1 class SampleClass
2 {
3 // Method that matches the TCDelegate signature.
4 public static void TCMethod(string message)
5 {
6 // Add code here.
7 }
8
9 // Method that instantiates the delegate.
10 void TCDelegate()
11 {
12 TCDelegate sd = tcMethod;
13 sd("Sample string");
14 }
15 }
Overall, Delegates are the vital signature methods for the validation of signatures between two methods. The above code must help you in using delegate in an error-free manner.