Ref vs Out Keywords in C#

What are Ref and Out Keywords?

In C#, the ref and out keywords are used to pass arguments by reference. This means that changes made to the parameter inside the method affect the argument used to call the method. However, there are key differences between ref and out.

Ref Keyword

The ref keyword is used to pass a variable by reference. The variable passed with ref must be initialized before it is passed to the method.

Example: Using the Ref Keyword

void ModifyValue(ref int number)
{
    number += 10;
}

int original = 5;
ModifyValue(ref original);
Console.WriteLine(original);  // Output: 15
        

In this example, the ref keyword is used to modify the original value of original. The value is updated inside the method and reflects the changes in the original variable.

Out Keyword

The out keyword is also used to pass variables by reference. However, unlike ref, the variable passed with out does not need to be initialized before it is passed to the method. The method must assign a value to the out parameter before the method returns.

Example: Using the Out Keyword

void GetValue(out int number)
{
    number = 20;
}

int result;
GetValue(out result);
Console.WriteLine(result);  // Output: 20
        

In this example, the out keyword is used to pass the variable result by reference. The method assigns a value to the variable, and the new value is reflected after the method call.

Difference Between Ref and Out

Although both ref and out are used to pass variables by reference, there are some important differences:

Key Points to Remember

• The ref keyword requires the variable to be initialized before passing it to a method.
• The out keyword allows passing uninitialized variables, but the method must assign a value before returning.
• Both ref and out pass arguments by reference, allowing the method to modify the original variable.