Tools: C# Conditional Statements (if, else, switch)

if Statement ## if - else Statement ## if - else if - else ## switch Statement ## User Input with Decision Structures ## Summary ## Menu Example: Using if, else if, else and switch Originally published at https://allcoderthings.com/en/article/csharp-decision-structures-if-else-switch In programming, you often need to perform different actions depending on conditions. In C#, such cases are handled with decision structures. The most common ones are if, else if, else, and switch. The if statement executes a block when the condition is true. Use else to run an alternative block when the condition is false. Check multiple conditions in sequence using else if. Use switch to branch execution based on fixed values. It is more readable than many else if blocks. Console.Write("Enter day number (1-7): "); int day = int.Parse(Console.ReadLine()); Decision structures often rely on user input. In this example, a simple console-based menu system is created. The user makes a choice, which is validated with the if / else if / else structure, and the switch statement executes the selected mathematical operation. This demonstrates how conditional and selection structures can be combined. Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well For further actions, you may consider blocking this person and/or reporting abuse COMMAND_BLOCK: int number = 10; if (number > 5) { Console.WriteLine("Number is greater than 5."); } Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: int number = 10; if (number > 5) { Console.WriteLine("Number is greater than 5."); } COMMAND_BLOCK: int number = 10; if (number > 5) { Console.WriteLine("Number is greater than 5."); } CODE_BLOCK: Console.Write("Enter your grade: "); int grade = int.Parse(Console.ReadLine()); // convert from string to int if (grade >= 50) { Console.WriteLine("You passed."); } else { Console.WriteLine("You failed."); } Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: Console.Write("Enter your grade: "); int grade = int.Parse(Console.ReadLine()); // convert from string to int if (grade >= 50) { Console.WriteLine("You passed."); } else { Console.WriteLine("You failed."); } CODE_BLOCK: Console.Write("Enter your grade: "); int grade = int.Parse(Console.ReadLine()); // convert from string to int if (grade >= 50) { Console.WriteLine("You passed."); } else { Console.WriteLine("You failed."); } CODE_BLOCK: int grade = 75; if (grade >= 90) { Console.WriteLine("Grade: A"); } else if (grade >= 70) { Console.WriteLine("Grade: B"); } else if (grade >= 50) { Console.WriteLine("Grade: C"); } else { Console.WriteLine("Failed"); } Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: int grade = 75; if (grade >= 90) { Console.WriteLine("Grade: A"); } else if (grade >= 70) { Console.WriteLine("Grade: B"); } else if (grade >= 50) { Console.WriteLine("Grade: C"); } else { Console.WriteLine("Failed"); } CODE_BLOCK: int grade = 75; if (grade >= 90) { Console.WriteLine("Grade: A"); } else if (grade >= 70) { Console.WriteLine("Grade: B"); } else if (grade >= 50) { Console.WriteLine("Grade: C"); } else { Console.WriteLine("Failed"); } CODE_BLOCK: switch (day) { case 1: Console.WriteLine("Monday"); break; case 2: Console.WriteLine("Tuesday"); break; case 3: Console.WriteLine("Wednesday"); break; case 4: Console.WriteLine("Thursday"); break; case 5: Console.WriteLine("Friday"); break; case 6: Console.WriteLine("Saturday"); break; case 7: Console.WriteLine("Sunday"); break; default: Console.WriteLine("Invalid day!"); break; } Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: switch (day) { case 1: Console.WriteLine("Monday"); break; case 2: Console.WriteLine("Tuesday"); break; case 3: Console.WriteLine("Wednesday"); break; case 4: Console.WriteLine("Thursday"); break; case 5: Console.WriteLine("Friday"); break; case 6: Console.WriteLine("Saturday"); break; case 7: Console.WriteLine("Sunday"); break; default: Console.WriteLine("Invalid day!"); break; } CODE_BLOCK: switch (day) { case 1: Console.WriteLine("Monday"); break; case 2: Console.WriteLine("Tuesday"); break; case 3: Console.WriteLine("Wednesday"); break; case 4: Console.WriteLine("Thursday"); break; case 5: Console.WriteLine("Friday"); break; case 6: Console.WriteLine("Saturday"); break; case 7: Console.WriteLine("Sunday"); break; default: Console.WriteLine("Invalid day!"); break; } CODE_BLOCK: Console.Write("Enter a number: "); int number = int.Parse(Console.ReadLine()); if (number % 2 == 0) { Console.WriteLine("The number is even."); } else { Console.WriteLine("The number is odd."); } Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: Console.Write("Enter a number: "); int number = int.Parse(Console.ReadLine()); if (number % 2 == 0) { Console.WriteLine("The number is even."); } else { Console.WriteLine("The number is odd."); } CODE_BLOCK: Console.Write("Enter a number: "); int number = int.Parse(Console.ReadLine()); if (number % 2 == 0) { Console.WriteLine("The number is even."); } else { Console.WriteLine("The number is odd."); } CODE_BLOCK: using System; class Program { static void Main() { Console.WriteLine("=== Menu ==="); Console.WriteLine("1 - Addition"); Console.WriteLine("2 - Subtraction"); Console.WriteLine("3 - Multiplication"); Console.WriteLine("4 - Division"); Console.WriteLine("0 - Exit"); Console.Write("Enter your choice: "); int choice = int.Parse(Console.ReadLine()); // convert from string to int if (choice == 0) { Console.WriteLine("Exiting program..."); } else if (choice >= 1 && choice <= 4) { Console.Write("Enter the first number: "); double num1 = double.Parse(Console.ReadLine()); Console.Write("Enter the second number: "); double num2 = double.Parse(Console.ReadLine()); switch (choice) { case 1: Console.WriteLine($"Result: {num1 + num2}"); break; case 2: Console.WriteLine($"Result: {num1 - num2}"); break; case 3: Console.WriteLine($"Result: {num1 * num2}"); break; case 4: if (num2 != 0) Console.WriteLine($"Result: {num1 / num2}"); else Console.WriteLine("Error: Division by zero is not allowed!"); break; } } else { Console.WriteLine("Invalid choice."); } } } Enter fullscreen mode Exit fullscreen mode CODE_BLOCK: using System; class Program { static void Main() { Console.WriteLine("=== Menu ==="); Console.WriteLine("1 - Addition"); Console.WriteLine("2 - Subtraction"); Console.WriteLine("3 - Multiplication"); Console.WriteLine("4 - Division"); Console.WriteLine("0 - Exit"); Console.Write("Enter your choice: "); int choice = int.Parse(Console.ReadLine()); // convert from string to int if (choice == 0) { Console.WriteLine("Exiting program..."); } else if (choice >= 1 && choice <= 4) { Console.Write("Enter the first number: "); double num1 = double.Parse(Console.ReadLine()); Console.Write("Enter the second number: "); double num2 = double.Parse(Console.ReadLine()); switch (choice) { case 1: Console.WriteLine($"Result: {num1 + num2}"); break; case 2: Console.WriteLine($"Result: {num1 - num2}"); break; case 3: Console.WriteLine($"Result: {num1 * num2}"); break; case 4: if (num2 != 0) Console.WriteLine($"Result: {num1 / num2}"); else Console.WriteLine("Error: Division by zero is not allowed!"); break; } } else { Console.WriteLine("Invalid choice."); } } } CODE_BLOCK: using System; class Program { static void Main() { Console.WriteLine("=== Menu ==="); Console.WriteLine("1 - Addition"); Console.WriteLine("2 - Subtraction"); Console.WriteLine("3 - Multiplication"); Console.WriteLine("4 - Division"); Console.WriteLine("0 - Exit"); Console.Write("Enter your choice: "); int choice = int.Parse(Console.ReadLine()); // convert from string to int if (choice == 0) { Console.WriteLine("Exiting program..."); } else if (choice >= 1 && choice <= 4) { Console.Write("Enter the first number: "); double num1 = double.Parse(Console.ReadLine()); Console.Write("Enter the second number: "); double num2 = double.Parse(Console.ReadLine()); switch (choice) { case 1: Console.WriteLine($"Result: {num1 + num2}"); break; case 2: Console.WriteLine($"Result: {num1 - num2}"); break; case 3: Console.WriteLine($"Result: {num1 * num2}"); break; case 4: if (num2 != 0) Console.WriteLine($"Result: {num1 / num2}"); else Console.WriteLine("Error: Division by zero is not allowed!"); break; } } else { Console.WriteLine("Invalid choice."); } } } - if: Runs when condition is true. - else: Runs when condition is false. - else if: Checks multiple conditions sequentially. - switch: Branches on fixed values.