Abstract C#

C# > Keywords > abstract

Abstract  indicates that a class is intended only to be a base class of other classes.
Abstract classes features:

• cannot be instantiated.
• may contain abstract methods and accessors.
• it is not possible to modify an abstract class with the sealed modifier
• class derived from an abstract class must include actual implementations of all inherited abstract methods and accessors.

Example:

    public abstract class Shape

    {
        public abstract int Area();
    }
    public class Rectangle : Shape
    {
        int x = 0;
        int y = 0;
        public Rectangle(int _x, int _y)
        {
            x = _x;
            y = _y;
        }
        public override int Area()
        {
            return x * y;
        }
    }

    Rectangle rct = new Rectangle(10, 20);
    int area = rct.Area();

Modifiers C#

C# > Modifiers

Modifiers are used to modify declarations of types and type members.

• Access Modifiers
• protected
• abstract
• readonly
• const
• sealed

GetRandomFileName C#

C# > Files > GetRandomFileName

GetRandomFileName returns a random cryptographically string that can be used as either a folder name or a file name. GetRandomFileName does not create a file.

 

Example:
string rndFile = Path.GetRandomFileName();

Working with files in C#

C# > IO

IO allow reading and writing to files and data streams, and types that provide basic file and directory support.

Directory class

Path methods

• GetTempPath
• GetRandomFilename
• GetFileName

IO

• Read-write binary
• MemoryStream
• Ports
• FileInfo Class
• File Class
• DirectoryInfo

Examples:

• Search for files

String Type C#

C# > Types > String

String type represents a sequence of Unicode characters and is a reference type.

Methods

• StartWith

Example:

string a = "Hello";
string b = " world";
// Append ! to contents of b
b += "!";
MessageBox.Show (a + b);

What is C#

C# is modern, multi-paradigm,  strongly-typed, object oriented  and high level programming language.
C# is an elegant language that enables you to build a variety of secure and robust applications that run on the .NET Framework. With C# you can create Windows client or Web applications, XML Web services, distributed components, client-server applications, database applications, etc.

The language of C# is very easy for anyone familiar with C, C++ or Java.

• Types
• Keywords
• Reflection
• Delegates
• Generics
• LINQ
• Modifiers
• Files & IO
• InteropServices
• Indexers
• Operators
• Printing
• Serialization
• Statements
• System
• Controls
• Cursors
• Text
• Form
• Design patterns

System

• .Net
• Diagnostics
• System.Data
• Security
• XML

Reflection C#

C# > Reflection 

Reflection offers the possibility   to describe assemblies, modules and types. It enables you to access the attributes. 
A compiled C# program is a relational database called metadata.

• Find classes implementing interface

Example:

using System;

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace csharp

{
    public partial class Form1 : Form
    {
        public static int mNumber = 10;
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            Type objType = typeof(Form1);
            FieldInfo field = objType.GetField("mNumber");
            object objValue = field.GetValue(null);
            MessageBox.Show(objValue.ToString());
        }
    }
}