CSharp Statements and Expressions

CSharp Statements and Expressions

In C# a statement is a line of code which form part of the program flow. Each line of code may perform an action or it may contain a non-action piece of code. Lets see how many types of C# statements we may write and then we will see a complete program using all these types of statements.

Types of Statements

1. Declare Statements
2. Assignment Statements
3. Function Call Statements
4. Return Statements
5. Break Statement
6. Conditional Statements
7. Loop Statements

Expressions in C# are a combination of one or more variables, operators, a function call that would be processed and gives back a value. This value may be used by other expressions or contexts. Below are few examples of expressions

• a>10
• x = 2+3;
• counter == 100
• Math.Pow(2,4);

Lets try to understand them with example program. You can copy this program into a Visual Studio Console Application Project. Copy the code into Program.cs file and you are good to go. Hit F5 and you have an interactive application.

Example:

using System;
namespace SampleConsoleApp
{
    class Program
    {
        static void Main()
        {

            //Declare Statements
            double counter;

            string DoWhat; //1: Calculate Power, 2: Mutiply

            //Assignment Statements 
            counter = 10;
            DoWhat = "";

            while (true)
            {
                Console.WriteLine("");
                Console.WriteLine("Press One of these Options");
                Console.WriteLine("1. Power Calculation");
                Console.WriteLine("2. Multiples");
                Console.WriteLine("3. Say Hello");
                Console.WriteLine("0. Exit");
                DoWhat = Console.ReadLine();

                Console.WriteLine("You selected " + DoWhat);

                if (DoWhat.Equals("1"))  //Conditional Statements
                {
                    for (double i = 0; i < counter; i++) //Loop Statement and Expressions
                    {
                        PrintPower(i, (i - 2)); //Function Call Statement
                    }
                }
                else if (DoWhat.Equals("2"))  //Conditional Statements
                {
                    for (int times = 0; times < 5; times++) //Loop Statement
                    {
                        PrintMultiples(times, 6);//Function Call Statement
                    }
                }
                else if (DoWhat.Equals("3"))  //Conditional Statements
                {
                    SayHello();
                }
                else if (DoWhat.Equals("0"))  //Conditional Statements
                {
                    break; //Break Statement
                }
                else  //Conditional Statements
                {
                    Console.WriteLine("Invalid Input. Try Again");
                }
            }

            Environment.Exit(0);
        }

        private static void SayHello()
        {
            Console.WriteLine("Hello There");
        }

        private static void PrintMultiples(int i, int j)
        {
            Console.WriteLine("{0} x {1} = {2}", i, j, i * j);
        }

        private static void PrintPower(double i, double PowerOf)
        {
            try
            {
                Console.WriteLine("{0} to the power of {1} is {2}", i, PowerOf, Math.Pow(i, PowerOf));
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                Console.WriteLine("Press Enter to EXIT");
                Console.ReadLine();
                Environment.Exit(1);
            }
        }
    }
}

Here is the program output

CSharp Your first CSharp program dissected

Your first CSharp program

Hello and Welcome to this C# multi-part series. We are going to start from the basics of C# language and get down to coding without getting deep into the history.


What you need to write and run the programs:
Download Free Visual Studio Community edition





















This is our first C# sample program.

 using System;
 namespace SampleConsoleApp
 {
   class Program
   {
      static void Main(string[] args)
      {
         Console.WriteLine("Hello World");
         Console.ReadLine();
     }
   }
 }

Lets dissect it for a moment line by line.

1 using System; 

This is the bare minimum required by a C# executable. The statement means I want to use the namespace "System" and everything in it. Whats a namespace? Its a logical division of an application. Your code can exist in a single name space or span many. We will get to that in the next tutorials.

2 namespace SampleConsoleApp

This is my programs namespace called "SampleConsoleApp". This namespace contains the code that I wrote. 

3 {

Starting of my namespace "SampleConsoleApp"

4   class Program
I am declaring a class called Progam. You can use any name you like. Classes are simply template for objects that you create when needed. We will discuss classes and objects later in the course as part of object oriented programming.

5   {
Start of my namespace "Program"

6      static void Main(string[] args)
This is the entry point to the program. You can have only one Main method in this type of application. The string[] args is used to pass data that your program may need to run. You can also skip writing 

7      {
Start of my Main method

8         Console.WriteLine("Hello World");
Prints "Hello World" on the console.

9         Console.ReadLine();
Makes your program to wait for an input <ENTER>.

10      }
Ending of Main method

11   }
Ending of my namespace "Program"

12 }
Ending of my namespace "SampleConsoleApp"

To run this program just hit Ctrl+F5 or goto Debug menu and select Start Without Debugging on your visual studio and you should see "Hello World" on the console window.



Happy programming.

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