What is difference between using if/else and switch-case in C#?

The switch statement and if-else statements are both selection statements in C# used for decision-making, but they serve different purposes and have distinct performance characteristics. The switch statement chooses a single section to execute from a list of candidates based on pattern matching, while if-else provides conditional branching based on boolean expressions.

Syntax

Following is the syntax for a switch statement −

switch (expression) {
    case value1:
        // code block
        break;
    case value2:
        // code block
        break;
    default:
        // default code block
        break;
}

Following is the syntax for if-else statements −

if (condition1) {
    // code block
} else if (condition2) {
    // code block
} else {
    // default code block
}

Using Switch Statement

The switch statement is ideal when you need to compare a single variable against multiple constant values −

using System;

class Program {
    public enum Fruits { Red, Green, Blue }
    
    public static void Main() {
        Fruits c = (Fruits)(new Random()).Next(0, 3);
        
        switch (c) {
            case Fruits.Red:
                Console.WriteLine("The Fruits is red");
                break;
            case Fruits.Green:
                Console.WriteLine("The Fruits is green");
                break;
            case Fruits.Blue:
                Console.WriteLine("The Fruits is blue");
                break;
            default:
                Console.WriteLine("The Fruits is unknown.");
                break;
        }
    }
}

The output of the above code is −

The Fruits is green

Using If-Else Statements

The if-else approach provides the same functionality but uses sequential condition checking −

using System;

class Program {
    public enum Fruits { Red, Green, Blue }
    
    public static void Main() {
        Fruits c = (Fruits)(new Random()).Next(0, 3);
        
        if (c == Fruits.Red)
            Console.WriteLine("The Fruits is red");
        else if (c == Fruits.Green)
            Console.WriteLine("The Fruits is green");
        else if (c == Fruits.Blue)
            Console.WriteLine("The Fruits is blue");
        else
            Console.WriteLine("The Fruits is unknown.");
    }
}

The output of the above code is −

The Fruits is blue

Using If-Else for Complex Conditions

If-else statements excel when dealing with complex boolean conditions that switch cannot handle −

using System;

class Program {
    public static void Main() {
        int score = 85;
        int attendance = 92;
        
        if (score >= 90 && attendance >= 95) {
            Console.WriteLine("Grade: A+");
        } else if (score >= 80 && attendance >= 85) {
            Console.WriteLine("Grade: A");
        } else if (score >= 70) {
            Console.WriteLine("Grade: B");
        } else {
            Console.WriteLine("Grade: C");
        }
    }
}

The output of the above code is −

Grade: A

Performance and Use Cases

Comparison

Conclusion

Use switch statements when comparing a single variable against multiple constant values for better performance and cleaner code. Choose if-else statements for complex conditions involving ranges, logical operators, or multiple variables. The switch statement offers O(1) lookup time, making it significantly faster for scenarios with many constant comparisons.