C# if else constructs

In this chapter you will learn:

• What is if else constructs in C#?
• How to use if else in programming?
• What is nested if else constructs?

The if… else construct is used for determining the flow of program based on returning expression value. It evaluates the comparison operator and based on value executes the statements. For example, if you want to execute a piece of code when the requirements meet then if… else construct determine which piece of code will be executed. Else is default condition and executes when no if condition matches. The following example will clear the concept of if… else constructs.

If Else Programming Example

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace if_else
{
    class Program
    {
        static void Main(string[] args)
        {
            int opt, num1, num2;
            float result;

        label:

            Console.WriteLine("\n\tMenu");
            Console.WriteLine("\nPress 1 for add");
            Console.WriteLine("Press 2 for subtraction");
            Console.WriteLine("Press 3 for multiplication");
            Console.WriteLine("Press 4 for Division");

            Console.Write("\n\nEnter first number:\t");
            num1 = Convert.ToInt32(Console.ReadLine());

            Console.Write("Enter second number:\t");
            num2 = Convert.ToInt32(Console.ReadLine());

            Console.Write("\nEnter your option:\t");
            opt = Convert.ToInt32(Console.ReadLine());

            if (opt == 1)
            {
                result = num1 + num2;
                Console.WriteLine("\n{0} + {1} = {2}", num1, num2, result);
            }
            else if (opt == 2)
            {
                result = num1 - num2;
                Console.WriteLine("\n{0} - {1} = {2}", num1, num2, result);
            }
            else if (opt == 3)
            {
                result = num1 * num2;
                Console.WriteLine("\n{0} x {1} = {2}", num1, num2, result);
            }
            else if (opt == 4)
            {
                result = (float)(num1 / num2);
                Console.WriteLine("\n{0} / {1} = {2}", num1, num2, result);
            }
            else
            {
                Console.WriteLine("Invalid option. Try again");
                goto label;
            }
            Console.ReadLine();
        }
    }
}

Output

        Menu



Press 1 for add

Press 2 for subtraction

Press 3 for multiplication

Press 4 for Division



Enter first number :       16

Enter second number :   5



Enter your option:          4



16 / 5 = 3.2
__

If you have more than one if construct then you can use else if construct for evaluating expression. The C# also supports nested if else construct. If you want to evaluate certain condition based on previous if, then you can use nested if-else constructs in C# programming.

Summary

In this chapter you learned about if else constructs as well as nested if else constructs. You also learned how to use if else conditional constructs in C# programming. In next chapter, you will learn about C# switch case constructs.