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up vote 25 down vote favorite
5

what is the most efficient way of turning the list of values of a dictionary into an array

for example, if i have:

Dictionary where key is string and value is Foo

i want to get Foo[]

I am using VS 2005, C# 2.0

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4 Answers

up vote 38 down vote accepted 
// dict is Dictionary<string, Foo>

Foo[] foos = new Foo[dict.Count];
dict.Values.CopyTo(foos, 0);

// or in C# 3.0:
var foos = dict.Values.ToArray();
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Does the extension .ToArray<Foo>() perform any better? – Goran Oct 13 '08 at 9:15
but how do we know that it's the most efficient ? – Tom Carter Oct 13 '08 at 9:16
   
I can't see how ToArray() could be any faster than the straight copy - which seems to be minimalistic. – Samuel Kim Oct 13 '08 at 9:18
@Tom I usually take the view that anything built into the framework (like .CopyTo() or .ToArray()) is the most efficient way to do it. The Microsofties are smarter than me. :) – Matt Hamilton Oct 13 '08 at 9:56
1  
ToArray is less performant than CopyTo (it uses CopyTo to copy to an internal intermediate representation, and then Copy again to return it out). However, as with all micro-performance related matters go for readability, robustness and maintainability and measure performance if it's an issue. – ICR Oct 13 '08 at 14:01
up vote 4 down vote

Store it in a list. It is easier;

List<Foo> arr = new List<Foo>(dict.Values);

Of course if you specifically want it in an array;

Foo[] arr = (new List<Foo>(dict.Values)).ToArray();
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up vote 3 down vote

There is a ToArray() function on Values:

Foo[] arr = new Foo[dict.Count];    
dict.Values.CopyTo(arr, 0);

But I don't think its efficient (I haven't really tried, but I guess it copies all these values to the array). Do you really need an Array? If not, I would try to pass IEnumerable:

IEnumerable<Foo> foos = dict.Values;
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up vote 0 down vote

If you would like to use linq, so you can try following:

Dictionary<string, object> dict = new Dictionary<string, object>();
var arr = dict.Select(z => z.Value).ToArray();

I don't know which one is faster or better. Both work for me.

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dict.Values.ToArray() does the same thing, but without the overhead of materializing each value through a delegate. – BACON Feb 21 at 13:56

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