How to read inputs as integers in C#?

To read inputs as integers in C#, you need to first read the input as a string using Console.ReadLine() and then convert it to an integer using methods like Convert.ToInt32() or int.Parse().

The process involves two steps: reading the user input as a string and converting it to an integer data type for mathematical operations.

Syntax

Following is the basic syntax for reading integer input −

string input = Console.ReadLine();
int number = Convert.ToInt32(input);

You can also use int.Parse() method −

int number = int.Parse(Console.ReadLine());

Using Convert.ToInt32() Method

The Convert.ToInt32() method converts the specified string representation of a number to an equivalent 32-bit signed integer. This method handles null values gracefully by returning 0.

Example

using System;

class Demo {
    static void Main() {
        Console.WriteLine("Enter a number: ");
        string input = Console.ReadLine();
        
        // Convert string to integer
        int number = Convert.ToInt32(input);
        
        // Perform calculations
        int doubled = number * 2;
        int squared = number * number;
        
        Console.WriteLine("You entered: " + number);
        Console.WriteLine("Doubled: " + doubled);
        Console.WriteLine("Squared: " + squared);
    }
}

The output of the above code when user enters 5 −

Enter a number: 
You entered: 5
Doubled: 10
Squared: 25

Using int.Parse() Method

The int.Parse() method directly converts a string to an integer. It is more strict than Convert.ToInt32() and throws an exception for null values.

Example

using System;

class Program {
    static void Main() {
        Console.WriteLine("Enter first number: ");
        int num1 = int.Parse(Console.ReadLine());
        
        Console.WriteLine("Enter second number: ");
        int num2 = int.Parse(Console.ReadLine());
        
        int sum = num1 + num2;
        int product = num1 * num2;
        
        Console.WriteLine("Sum: " + sum);
        Console.WriteLine("Product: " + product);
    }
}

The output of the above code when user enters 8 and 3 −

Enter first number: 
Enter second number: 
Sum: 11
Product: 24

Using TryParse() for Error Handling

The int.TryParse() method provides a safe way to convert strings to integers without throwing exceptions for invalid input.

Example

using System;

class SafeInput {
    static void Main() {
        Console.WriteLine("Enter a number: ");
        string input = Console.ReadLine();
        
        if (int.TryParse(input, out int result)) {
            Console.WriteLine("Valid number: " + result);
            Console.WriteLine("Number + 10 = " + (result + 10));
        } else {
            Console.WriteLine("Invalid input. Please enter a valid integer.");
        }
    }
}

The output of the above code when user enters "abc" −

Enter a number: 
Invalid input. Please enter a valid integer.

Comparison of Methods

Conclusion

Reading integer inputs in C# requires converting string input from Console.ReadLine() to integer using Convert.ToInt32(), int.Parse(), or int.TryParse(). For robust applications, use int.TryParse() to handle invalid input gracefully without exceptions.