C# 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 construct

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using System;

namespace if_else_construct
{
  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();           
      }
   }
}

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Output

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        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

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