How to use IF Loop in C#

How to use IF Loop in C#

• IF Loop in C# takes a Boolean expression as a condition and if this condition is TRUE, the compiler executes the code inside IF loop { } and if the condition is wrong, the compiler simply ignores the code.
• Here's the syntax of IF Loop in C#:

if (boolean-expression)
{
	// Code will come here, execute if the Condition is TRUE.
}

• Let's create a simple program, where we ask the user to enter his Physics marks and the program will tell the user whether he is passed or failed.
• I have used If loop and the condition I have used is, if the marks are less than 50 then student has failed & if its equal or greater than 50 then the user has passed.
• Here's the code for IF loop in C#, shown in below figure:

• You can see in above figure that I have entered 25, now when the compiler will come to first IF loop, it will check the condition (Marks >= 50), which is not true as the number we entered is less than 50, so the compiler will simply ignore this IF loop and will move on to second IF Loop.
• The condition in second IF Loop is (Marks < 50), and clearly this condition is TRUE, so our compiler will enter in this IF Loop, enclosed by curly brackets { }, and will print out "You failed the exam.".
• So, in simple words:
  • IF condition is TRUE  => Execute.
  • IF condition is FALSE => Ignore.
• Few commonly used conditional operators of IF Loops are:
  • Equal to ( == )
  • Not Equal to ( != )
  • Greater than ( > )
  • Less than ( < )
  • Greater than or Equal to ( >= )
  • Less than or Equal to ( <= )
• We could also use multiple conditions in single IF Loop using these two operators:
  • && ( AND ) => it returns TRUE, if both conditions are TRUE.
  • || ( OR ) => it returns TRUE, if either of two conditions is TRUE.
• Let's edit out code a little and add a 3rd condition, as shown in below figure:

• Here, I have used three IF Loops in above code and have used && operator in second IF Loop.
• So, if the number is in between 50 & 90, then second loop will execute, both conditions have to be TRUE.
• I hope you have understood How to use IF Loop in C#, now let's move a little forward and have a look at IF Else Loop in C#, which is kind of an extension of IF Loop.

IF-Else Loop in C#

• Instead of using separate IF Loops for different conditions, we can use single IF-Else Loop.
• In our first code, we have used two IF Loops to check whether student has passed or failed.
• Let's rewrite that code using IF-Else Loop, as shown in below figure:

• As you can see in above figure, first I have used IF Loop and placed a condition that if (Marks >= 50) then print "you passed the exam" otherwise simply print "you failed the exam".
• Else condition is like the default option, if "IF" Loop failed to execute then "ELSE" will be executed and if "IF" loop is successful, then "ELSE" will be ignored.
• That was the case for two IF Loops, but what if we have more than two IF Loops, as in our second code, we have 3 IF Loops, let's rewrite that code using IF-Else Loop:

• The above code is working exactly the same as our code with 3 IF Loops but here we are using IF-Else Loop.
• In IF-Else Loop, the first loop will be "if" loop and the last one will be "else" loop while all the intermediary loops will be "else if" loops.
• Here's the final code for today's lecture:

using System;

namespace TEPProject
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter your Physics marks: ");
            int Marks = int.Parse(Console.ReadLine());

            if (Marks >= 90)
            {
                Console.WriteLine("You got A+ grade. \n\n");
            }
            else if (Marks >= 50 && Marks < 90)
            {
                Console.WriteLine("You passed the exam. \n\n");
            }
            else
            {
                Console.WriteLine("You failed the exam. \n\n");
            }

        }
    }
}