Constructing an array out of existing arrays in C# - will this create copies in memory?

Question

In my C# code, I have constructed four arrays of data:

double[] values;
DateTime[] timestamps;
long[] qualities;
long[] reasons;

These arrays need to be passed to an external API. The API method call is somewhat indirect; its signature looks like invokeApiMethod(string apiMethodName, Object[] apiMethodParams).

In this case, the external API method call expects four arrays of the kind that I have already constructed.

If I construct the Object[] using the following code:

Object[] apiMethodParams = { values, timestamps, qualities, reasons };

Will this result in all four existing arrays being copied into a large contiguous block of new memory? Or will C# just pass an array of references to the existing arrays to the external API?

Jon Skeet · Accepted Answer · 2012-05-10 05:51:01Z

4

Will this result in all four existing arrays being copied into a large contiguous block of new memory? Or will C# just pass an array of references to the existing arrays to the external API?

The latter. It will be an array of four elements, each element of which is a reference. The values of values, timestamps etc are just references to arrays.

Note that you may want to take a copy of some or all of the arrays if the external API modifies the array contents, and you want the original values - but that won't happen automatically.

answered May 10, 2012 at 5:51

Jon Skeet

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Tilak · Accepted Answer · 2012-05-10 05:54:33Z

1

http://www.mbaldinger.com/post/C-reference-types-are-passed-by-value!.aspx

http://answers.yahoo.com/question/index?qid=20090105141923AAt63hD

In case you need to pass different array, you need to clone/copy it and then pass the cloned/copied array

answered May 10, 2012 at 5:54

Tilak

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iefpw · Accepted Answer · 2012-05-10 06:21:25Z

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They are references. Copying and creating uses the "new" keyword.

answered May 10, 2012 at 6:21

iefpw

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