Decision Making in C#: If, Else and Switch

Imagine you’re a teacher grading exams. If a student scores above 90, you give an A. If they score above 80, you give a B. If they fail, you give an F.

These are decisions, simple, everyday decisions.

Computers also make decisions, but they follow strict rules.
Today, you’ll teach C# how to choose different actions based on different conditions, just like a real teacher (but much faster!).

By the end of this lesson, you’ll build a complete Grading System App.

The Project: Grading System App

Your program will ask the user for a score and print a grade:

text

5 lines

23/ 500 tokens

1
2
3
4
5
========================
   GRADING SYSTEM
   Score: 87
   Grade: B
========================

Let’s learn the tools needed to make this work. Conditional logic allows your program to run different code depending on what is true.

C# offers several ways to do this:

if
else if
else
switch

These are the brain of your program, the part that thinks.

The If Statement

The simplest form:

csharp

4 lines

12/ 500 tokens

1
2
3
4
if (score > 90)
{
    Console.WriteLine("A");
}

Code Tools

This only runs if the condition is true.

If–Else Chain

Use this when you have multiple conditions:

csharp

12 lines

35/ 500 tokens

1
2
3
4
5
6
7
8
9
10
11
12
if (score >= 90)
{
    Console.WriteLine("A");
}
else if (score >= 80)
{
    Console.WriteLine("B");
}
else
{
    Console.WriteLine("F");
}

Code Tools

Only one of these blocks will run.

Nested Conditions

You can put one if inside another to create more detailed checks:

csharp

5 lines

21/ 500 tokens

1
2
3
4
5
if (score >= 60)
{
    if (score >= 90)
        Console.WriteLine("Excellent!");
}

Code Tools

But use nesting only when needed, too much makes code harder to read.

Switch Statement

A switch checks one value and chooses from many cases.

Example:

csharp

14 lines

57/ 500 tokens

1
2
3
4
5
6
7
8
9
10
11
12
13
14
switch (option)
{
    case 1:
        Console.WriteLine("Start game");
        break;

    case 2:
        Console.WriteLine("Settings");
        break;

    default:
        Console.WriteLine("Invalid choice");
        break;
}

Code Tools

Great for designing menus and category-based decisions.

Let’s Build the Grading System App

Here is the complete program:

csharp

29 lines

177/ 500 tokens

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Enter your score:");
        int score = Convert.ToInt32(Console.ReadLine());

        string grade;

        if (score >= 90)
            grade = "A";
        else if (score >= 80)
            grade = "B";
        else if (score >= 70)
            grade = "C";
        else if (score >= 60)
            grade = "D";
        else
            grade = "F";

        Console.WriteLine("========================");
        Console.WriteLine("   GRADING SYSTEM");
        Console.WriteLine($"   Score: {score}");
        Console.WriteLine($"   Grade: {grade}");
        Console.WriteLine("========================");
    }
}

Code Tools

This program makes a decision every time based on user input.

How It Works

User enters a score.
Program checks each condition in order.
As soon as one condition is true, the matching grade is assigned.
Output is printed as a formatted card.

Test it in the DevsCall AI Online Runner to see how it responds to different scores.

Learn Together with AI

Try these prompts with your AI Copilot:

“Rewrite the grading system using switch instead of if–else.”
“Add + and – grades (A+, B-, etc.).”
“Explain nested conditions with real examples.”
“Make a version that handles invalid input safely.”

AI will help you expand your logic step-by-step.

Practice Time

Create a program that:

Asks the user to choose an operation:
1. Add
2. Subtract
3. Multiply
4. Divide
Then uses switch to perform the correct action.

Expected menu:

text

7 lines

27/ 500 tokens

1
2
3
4
5
6
7
========================
   SIMPLE MENU
1. Add
2. Subtract
3. Multiply
4. Divide
========================

Use switch to handle user choices cleanly.

Example Solution

csharp

37 lines

258/ 500 tokens

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("========================");
        Console.WriteLine("   SIMPLE MENU");
        Console.WriteLine("1. Add");
        Console.WriteLine("2. Subtract");
        Console.WriteLine("3. Multiply");
        Console.WriteLine("4. Divide");
        Console.WriteLine("========================");
        Console.WriteLine("Choose an option:");

        int option = Convert.ToInt32(Console.ReadLine());

        switch (option)
        {
            case 1:
                Console.WriteLine("You chose Add.");
                break;
            case 2:
                Console.WriteLine("You chose Subtract.");
                break;
            case 3:
                Console.WriteLine("You chose Multiply.");
                break;
            case 4:
                Console.WriteLine("You chose Divide.");
                break;
            default:
                Console.WriteLine("Invalid choice.");
                break;
        }
    }
}

Code Tools

If your version behaves the same, congratulations, your program can think!

Previous Lesson Next Lesson

Frequently Asked Questions

Use if–else when you have multiple conditions that must be checked in order, such as assigning grades or validating input.

Nested conditions occur when one if-statement is placed inside another to create more detailed decision paths.

break prevents the program from running into the next case accidentally. It stops the current case once it's executed.

Yes. In C#, switch can compare strings, characters, and numbers.

The default case runs, which is useful for catching invalid input or unexpected values.

Still have questions?Contact our support team