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ICollection.CopyTo() vs. ArrayList.ToArray()

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Dear all,

I want to convert a ICollection instance to a normal array. But then I realized these two ways will give me a Array object.
Just curious, which one is better (efficient in memory or faster).

I usually use CopyTo as follows: (assume we have ICollection collection has been initialized)

object[] array = new object[collection.Size];
collection.CopyTo(array, 0);

And for ToArray()
object[] array = new ArrayList(collection).ToArray();

Thank you,
idos

2007년 8월 4일 토요일 오후 4:08

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Hi Idos,

The ArrayList, Queue, and Stack types contain overloaded CopyTo( ) and ToArray( ) methods for copying their elements to an array.

The CopyTo( ) method copies its elements to an existing one-dimensional array, overwriting the contents of the array beginning at the index you specify.

The ToArray( ) method returns a new array with the contents of the type's elements.

Thus, as far as I know, the CopyTo( ) method is better.

In the case of a ArrayList, ToArray( ) would return a new array containing the elements in the ArrayList. CopyTo( ) would copy the ArrayList over a pre-existing array.

Copying from a Collection Type to an Array

Best Regards,

Martin Xie

2007년 8월 6일 월요일 오후 2:11
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Using ICollection.CopyTo() is far more efficient. When you use ArrayList, you'll make a duplicate of the collection and iterate it twice.

2007년 8월 6일 월요일 오후 3:20

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Hi Idos,

The ArrayList, Queue, and Stack types contain overloaded CopyTo( ) and ToArray( ) methods for copying their elements to an array.

The CopyTo( ) method copies its elements to an existing one-dimensional array, overwriting the contents of the array beginning at the index you specify.

The ToArray( ) method returns a new array with the contents of the type's elements.

Thus, as far as I know, the CopyTo( ) method is better.

In the case of a ArrayList, ToArray( ) would return a new array containing the elements in the ArrayList. CopyTo( ) would copy the ArrayList over a pre-existing array.

Copying from a Collection Type to an Array

Best Regards,

Martin Xie

2007년 8월 6일 월요일 오후 2:11
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Using ICollection.CopyTo() is far more efficient. When you use ArrayList, you'll make a duplicate of the collection and iterate it twice.

2007년 8월 6일 월요일 오후 3:20
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wow thank you for the explanation ....

2007년 8월 9일 목요일 오전 1:53
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array.CopyTo(T[] target, int i) copies the values from array into target, starting at index i

array.ToArray() creates a buffer and and then calls CopyTo() internally

They are basically the same from a performance perspective and I would recommend ToArray() is most use-cases
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