I have recently started to learned about classes and objects in C♯. In one of my lectures, Rob Miles mentioned that passing by reference introduced a slight performance hit, and I decided to test this.

Here is the code I used:

using System;
using System.Diagnostics;

class ValueVsReference
{
    public static void SetValue(int somenumber, int maxi)
    {
        for (int i = 0; i < maxi; i++)
        {
            somenumber = i;
        }
    }

    public static void SetReference(ref int somenumber, int maxi)
    {
        for(int i = 0; i < maxi; i++)
        {
            somenumber = i;
        }
    }

    public static void Main()
    {
        int iterations = 100000;
        int a = 0;
        Console.Write("Iterations: {0} ", iterations);

        Console.Write("Value: ");
        Stopwatch valuetime = new Stopwatch();
        valuetime.Start();
        SetValue(a, iterations);
        valuetime.Stop();
        Console.Write("{0} ", valuetime.Elapsed);

        Console.Write("Reference: ");
        Stopwatch referencetime = new Stopwatch();
        referencetime.Start();
        SetReference(ref a, iterations);
        referencetime.Stop();
        Console.WriteLine(referencetime.Elapsed);
    }
}

(gist: https://gist.github.com/sbrl/b10bf5c765630562431f)

The results for 10,000 iterations can be found in this pastebin.

Average times:

• Value: 0.0000885
• Reference: 0.00009295

Final result: References are indeed slower than values, by ~5% (100 - ((0.00009295/0.0000885)*100)). Normally you would not need to worry about this performance drop though since it is so small.