Guid.Parse() or new Guid() - What's the difference?

Question

What is the difference between these two ways of converting a string to System.Guid? Is there a reason to choose one over the other?

var myguid = Guid.Parse("9546482E-887A-4CAB-A403-AD9C326FFDA5");

or

var myguid = new Guid("9546482E-887A-4CAB-A403-AD9C326FFDA5");

Accommodative

in terms of what ? – Preparator

You can also use : Guid.TryParse() – Modality

Answer 1

A quick look in the Reflector reveals that both are pretty much equivalent.

public Guid(string g)
{
    if (g == null)
    {
       throw new ArgumentNullException("g");
    }
    this = Empty;
    GuidResult result = new GuidResult();
    result.Init(GuidParseThrowStyle.All);
    if (!TryParseGuid(g, GuidStyles.Any, ref result))
    {
        throw result.GetGuidParseException();
    }
    this = result.parsedGuid;
}

public static Guid Parse(string input)
{
    if (input == null)
    {
        throw new ArgumentNullException("input");
    }
    GuidResult result = new GuidResult();
    result.Init(GuidParseThrowStyle.AllButOverflow);
    if (!TryParseGuid(input, GuidStyles.Any, ref result))
    {
        throw result.GetGuidParseException();
    }
    return result.parsedGuid;
}

Occlude

Thanks for the response. I was really looking for "is their a difference in how they work". – Accommodative

Looks like there's a clear difference in the GuidParseThrowStyle used, so one could throw an error for input that the other will not. – Erotica

@Triynko: If you look at the code, you will see that they both throw for the same causes. The only difference is that if an OverflowException is thrown it will be encapsulated in a FormatException in case of Guid.Parse. – Ingmar

Answer 2

Use the version that is the most readable to you. The two are implemented almost exactly the same way.

The only real difference is that the constructor initializes itself to Guid.Empty before attempting the parse. However, the effective code is identical.

That being said, if the Guid is coming from user input, then Guid.TryParse would be better than either option. If this Guid is hard coded, and always valid, either of the above are perfectly reasonable options.

Monocycle

Answer 3

I tried performance on one milion guids and Guid.Parse seems to be a insignificantly faster. It made 10-20 milisecods difference of 800 miliseconds of total creation on my PC.

public class Program
{
    public static void Main()
    {
        const int iterations = 1000 * 1000;
        const string input = "63559BC0-1FEF-4158-968E-AE4B94974F8E";

        var sw = Stopwatch.StartNew();
        for (var i = 0; i < iterations; i++)
        {
            new Guid(input);
        }
        sw.Stop();

        Console.WriteLine("new Guid(): {0} ms", sw.ElapsedMilliseconds);

        sw = Stopwatch.StartNew();
        for (var i = 0; i < iterations; i++)
        {
            Guid.Parse(input);
        }
        sw.Stop();

        Console.WriteLine("Guid.Parse(): {0} ms", sw.ElapsedMilliseconds);
    }
}

And output:

new Guid(): 804 ms

Guid.Parse(): 791 ms

Paratroops

This isn't a statistically significant benchmark. I ran this multiple times and got varying results. The background noise clouds any possible performance differences in these implementations. – Mullein

Answer 4

In .Net framework v1.1 exists only 1 way -> var myguid = new Guid("9546482E-887A-4CAB-A403-AD9C326FFDA5");

Guid.Parse became available later.

Aerobe

Please provide an explanation along with solution so the user has a better understanding of what the code is doing. – Cellule