Reference Passing

Reference passing allows variable to be modified by the function it's passed to.

Passing By Value

Let's look at the following example:

using System; namespace csharp { class Program { static void Main(string[] args) { int num = 0; incrementValue(num); Console.WriteLine(num); } static void incrementValue(int num) { num++; } } }

Output:

0

num is incremented by 1 in theincrementValue function. Since it's passed by value it remains 0 in the main function.

Passing By Reference

To pass by reference, the keyword ref needs to be added before argument in both function definition and call:

using System; namespace csharp { class Program { static void Main(string[] args) { int num = 0; incrementValue(ref num); Console.WriteLine(num); } static void incrementValue(ref int num) { num++; } } }

Output:

1

Since num is passed by reference at line 10, it's value has incremented inside the main function too.

Array Arguments

Arrays are always passed by reference.

using System; namespace csharp { class Program { static void Main(string[] args) { int[] arr = { 1, 2 }; modifyArray(arr); Console.Write(arr[0] + " " + arr[1]); } static void modifyArray(int[] arrayArg) { arrayArg[0] = 3; arrayArg[1] = 4; } } }

Output:

3 4

Though not specified via the ref keyword, array still gets modified by the function it's passed to.