How to convert Guid[] to String?

Question

Something like String.Join(",", new string[] { "a", "b" });, but for Guid[]

var guids = new Guid[] { Guid.Empty, Guid.Empty };

var str = /* Magic */

// str = 00000000-0000-0000-0000-000000000000,00000000-0000-0000-0000-000000000000

Palomo

Answer 1

var str = guids.Select(g => g.ToString())
               .Aggregate((working, next) => working + "," + next);

Once your list of Guids starts growing, this method of concatenation is going to cause performance issues. You can modify it to use a StringBuilder:

var str = guids.Select(g => g.ToString())
               .Aggregate(new StringBuilder(),
                          (sb, str) => sb.Append("," + str),
                          sb => sb.ToString());

Both of those are the complicated LINQ Extension method way of doing things. You could also simply use String.Join:

var str = String.Join(",", guids.Select(g => g.ToString()).ToArray());

Petcock

I'd be curious at how fast it works compared to other methods. I'm guessing Aggregate doesn't use String.Concat to allocate memory correctly. – Northwesterly

@Palomo - Just keep in mind that with large lists of Guids, you might run into perf issues (a lot of string concatenation). In that case, you might need to switch to the StringBuilder method (and manually remove the last comma). – Petcock

I will, but SO has a delay. Just wait 3 minutes :P – Palomo

@Yuriy Faktorovich - Aggregate will use whatever concatenation method you specify. – Petcock

@Justin Niessner: Right, but if you only pass two arguments to String.Concat it won't have any improvement over the + operator. The + operator I believe, don't quote me on this, already calls the String.Concat. – Northwesterly

Answer 2

.NET 4 added a String.Join<T>(string separator, IEnumerable<T> values method. So, in .NET 4, just this will work:

String.Join(",", guids);

Awn

Answer 3

String.Join(",", guids.Select(g => g.ToString()).ToArray());

Northwesterly

.NET 4 added a generic Join method which you can just pass the guids array to without modifications – Awn

Answer 4

I thought this would work?

StringBuilder stringBuilder = new StringBuilder();
int i = 0;
foreach (var guid in guids)
{
    stringBuilder.Append(guid.ToString());
    if (++i < guids.Length)
    { 
        stringBuilder.Append(","); 
    }
}

var str = stringBuilder.ToString();

Government

You forgot the , between GUIDs ;) – Cosmogony

That will put an extra comma at the end. – Northwesterly

Ok, I tried to fix the comma issue quickly. It's untested. I hope it works :-) – Government

as a suggestion, I would append the comma before appending the guid, but only if the stringbuilder.length > 0 – Wivinah

Answer 5

if your framework >= .NET 3.5

String.Join(",", (from g in guids select g.ToString()).ToArray())

Derman

Answer 6

String.Join(",", Array.ConvertAll(guids, g => g.ToString()));

Parlay

It seems this statement can't pass compilation in VS2010? – Unguent

Array.ConvertAll needs a class that implements Converter<TInput, TOutput>, you're passing in a method. – Northwesterly

Answer 7

//Convert string to List<string>    
List<string> guidList = your_string.Split(',').ToList<string>();

//Convert string to List<Guid>    
List<Guid> guidList = your_string.Split(',').ToList<string>().ConvertAll<Guid>(g => new Guid(g));

Ferree