I would like to select a range of items in an array of items. For example I have an array of 1000 items, and i would like to "extract" items 100 to 200 and put them in another array.
Can you help me how this can be done?
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2Make sure to accept an answer if it helps you.Matt Mitchell– Matt Mitchell2010-06-28 05:27:20 +00:00Commented Jun 28, 2010 at 5:27
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Does this answer your question? Array slices in C#Arkane– Arkane2023-03-08 17:08:29 +00:00Commented Mar 8, 2023 at 17:08
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1 Answer
In C# 8, range operators allow:
var dest = source[100..200];
(and a range of other options for open-ended, counted from the end, etc)
Before that, LINQ allows:
var dest = source.Skip(100).Take(100).ToArray();
or manually:
var dest = new MyType[100];
Array.Copy(source, 100, dest, 0, 100);
// source,source-index,dest,dest-index,count
3 Comments
robsn
It also has to be a core app. dot net 4.8 doesn't like it even if it's C#9, missing System.Range and System.Index.
redcalx
@MarcGravell It seems odd to me that array[1..10] creates a new array with a copy of the data (and appears to be syntactic shorthand for RuntimeHelpers.GetSubArray()); whereas span[1..10] gets a slice on that span (and is shorthand for .Slice()). I imagine this has come about due to legacy reasons, but to me it feels like it fails the "test of least astonishment".
Froggy
I find C#'s syntax of excluding the last item in the range unintuitive using the
source[100..200] syntax. Specifically, the OP asked items 100 to 200 to be extracted, which should include item 200, i.e. it is 101 items in total. @MarcGravell's solution excludes item 200.