C# out Keyword

The out keyword is also used to pass parameters by reference, but it is specifically used when the method is expected to return a value through the parameter. The key difference is that you don’t need to initialize the variable before passing it to the method. However, the method must assign a value to the out parameter before it exits.

Characteristics of out keyword

1. No Initialization Required: The variable does not need to be initialized before passing it to the method.

2. Must Be Assigned Inside Method: The method must assign a value to the out parameter before the method ends. You cannot leave the out parameter unassigned.

3. Used for Returning Multiple Values: It’s typically used when you need a method to return more than one value or a value when the result is uncertain (e.g., for TryParse methods).

Example:

using System;

class Calaculator
{
    public void getSum(int a, int b, out int sum)
    {
        sum = a + b;        // Assign a value to the out parameter
    }
    
    public void getSumAndProduct(int a, int b, out int totalSum, out int product)
    {
        totalSum = a + b; // Assign a value to the out parameter
        product = a * b; // Assign a value to the out parameter
    }
}

class MyExample
{
    static void Main(string[] args)
    {
        int sum, totalSum, product;
        Calaculator cal = new Calaculator();
        // Pass variables by reference using 'out'
        cal.getSum(5, 10, out sum);
        cal.getSumAndProduct(5, 10, out totalSum, out product);
        Console.WriteLine("Sum: " + sum);         // Output: Sum: 15
        Console.WriteLine("totalSum: " + totalSum);         // Output: totalSum: 15
        Console.WriteLine("product: " + product);         // Output: product: 50
    }
}

Output:

Explanation:

1. The sum, totalSum and product parameters are passed by reference using the out keyword.
2. The method assigns values to sum, totalSum and product, and these values are reflected outside the method.

C# out Keyword – Interview Questions

C# out Keyword – Objective Questions (MCQs)

void GetValues(out int x) { x = 5; }

Related C# out Keyword Topics