String.Format vs ToString()

Question

Can anyone explain if there is any benefit in either one of the following methods:

decimal d = 12.0m;

// 1. how I'd have done it
myLabel.Text = d.ToString();

// 2. how I saw someone do it today
myLabel.Text = String.Format("{0}", d);

Just to clarify, I'm not querying what the methods do, I'm obviously happy with that, just if there is perhaps a performance benefit in one over the other in this specific example. I'm aware of the added flexibility of cultures and formatting offered by string.format(), but I'd always just 'tostring()' numerics to attach their value to a label, or text based property in general.

To me, the string.format() option seems like more typing for no additional benefit here, but I wondered if there are any other 'under the hood' benefits of doing things one way vs the other.

Answer 1

I did a little benchmark in Linqpad:

void Main()
{
    int iterations = 1000000;
    decimal d = 12.0m;
    var text = "";

    var sw = Stopwatch.StartNew();
    for (int i = 0; i < iterations; i++)
    {
        // 1. how I'd have done it
        text = d.ToString();
    }
    sw.Stop();
    sw.ElapsedMilliseconds.Dump("ToString()");

    sw = Stopwatch.StartNew();
    for (int i = 0; i < iterations; i++)
    {
        // 2. how I saw someone do it today
        text = String.Format("{0}", d);
    }
    sw.Stop();
    sw.ElapsedMilliseconds.Dump("Format");
}

---

ToString() 157

Format 264

ToString() looks consistently faster.

EDIT: I should point out, that on my PC 10 million "Format" operations only took 2.2 seconds. This looks very much like a micro-optimization, and unless what you're doing is extremely performance-critical, or iterative - it'd not worry about this too much.