Ref vs Out Examples in C#

I know that many of my readers are just looking for their first job and taking part in job interviews, so it is probably worth discussing topics that you may be asked about during your job interview. Unfortunately, there are many such questions, in subsequent articles I will introduce you to more, but today I will show you how in C# you can pass a variable of a simple type to a method using references. Of course, for this purpose we will have to use the ref or out keywords and this article will show you how to use them and what the basic differences are between them.

What problem do we want to solve?

using System;

namespace Demo
{  
    class Program
    {
        static void Main()
        {
            int myNumber = 0;
            IncrementValue(myNumber);
            IncrementValue(myNumber);
            IncrementValue(myNumber);
            Console.WriteLine(myNumber);//0
        }

        public static void IncrementValue(int value)
        {
            value++;
        }
    }
}

Unfortunately, our variable was not incremented and still has the value 0. Why did this happen? The variable myNumber is of type int, and int is a simple type (value type), and therefore the value of the variable itself was passed to the IncrementValue method. In this case, the value of the myNumber variable is still the same. So how can we increase the value of the myNumber variable using the IncrementValue method? We need to pass the myNumber variable by reference to the IncrementValue method. To do this we need to use the ref or out keyword.

How to use the ref keyword?

using System;

namespace Demo
{  
    class Program
    {
        static void Main()
        {
            int myNumber = 0;
            IncrementValue(ref myNumber);
            IncrementValue(ref myNumber);
            IncrementValue(ref myNumber);
            Console.WriteLine(myNumber);//3
        }

        public static void IncrementValue(ref int value)
        {
            value++;
        }
    }
} 

How to use the out keyword?

using System;

namespace Demo
{  
    class Program
    {
        static void Main()
        {
            int myNumber;
            IncrementValue(out myNumber);
            IncrementValue(out myNumber);
            IncrementValue(out myNumber);
            Console.WriteLine(myNumber);//11
        }

        public static void IncrementValue(out int value)
        {
            value = 10;
            value++;
        }
    }
}

 As you can see, out doesn't make much sense in this case, but you can use it similarly to ref. This means that when you want to use the out keyword, you must mark the parameter in the signature with this word and when calling the method you must also precede the argument with the out keyword. Since initialization before passing to the method is unnecessary, you can also call the method this way:

static void Main()
{
    IncrementValue(out int myNumber);
    Console.WriteLine(myNumber);
}

ref vs out – what is the difference between ref and out?

• A variable marked with the word ref must be initialized before being passed as a parameter. In our case: "int number = 0;".
• A variable marked with the word out does not have to (but can) be initialized before being passed as a parameter. With us: "int number;". There may also be initialization before transfer, but this does not make any sense.
• A variable marked by ref does not need to be initialized in the method. In our case, only the following entry was allowed: "value++;".
• A variable marked with out must be initialized in the method. In our case, apart from incrementing, the variable had to be initialized first: "value = 10; value++;".

Which method should be used in which situation?

SUMMARY