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

Question

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

Answer 1

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

Answer 2

Using ICollection.CopyTo() is far more efficient.  When you use ArrayList, you'll make a duplicate of the collection and iterate it twice.

Answer 3

wow thank you for the explanation ....

 

Answer 4

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