Correct form to Slice an Array In C#

Question

i wanted to ask how to Slice an array without using Array.Copy. I'll give you an example of what i want to achieve so you can understand me.

Let's say i have this Array. called Original

[ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 ]

i want to get a copy array from an starting index given some length, lets say i want element one to element 6 i want the code to perform the task such as

int startIndex = 0;
int lenght= 5;
int[] CopyArray = ArrayFromRange(Original, startIndex, length);

then copyArray would be:

[ 1 | 2 | 3 | 4 | 5 ] i do not want to use Array.Copy because i will loop this to get subsequent slices

so i would do

int length = 3;
for(int i = 0; i < OriginalArray.Length; i++)
{
     int[] CopyArray = ArrayFromRange(OriginalArray, i, length);
     // perform some operations
}

This would give me an array of 4 elements every time the loop executes it and then I'd do some operations. But if I did Array.Copy it would throw an OutOfBoundsException when the i in the loop gets the value 13 it would try to copy the array[15] which does not exists. I want to avoid these kind of errors.

I'm developing on Winforms, .Net 4.0

Answer 1

I think the best way to treat your approach would be with IEnumerable objects, specifically using LINQ. IEnumerable is an interface meaning "you can call foreach on this object". It's implemented for arrays, and also for some other objects used to query collections - part of the point being, you don't especially need to know WHAT those objects are; just enumerate each item when you need them.

using System.Linq; // put this at the top of the .cs, not mid-code.

int startIndex = 0;
int lenght= 5;
IEnumerable<int> CopyArray = Original.Skip(startIndex).Take(lenght);

I wrote that in notepad, so it's possible there's some small thing I missed, but that should give you what you need. You can skip the .Skip(startIndex) part if it's always going to be 0. To access each int:

foreach (int value in CopyArray) {
   // TODO with value??
}

Answer 2

You can still use Array.Copy() but you just need to make sure that the index is within range:

T[] ArrayFromRange<T>(T[] originalArray, int startIndex, int length)
{
  int actualLength = Math.Min(length, originalArray.Length - startIndex);
  T[] copy = new T[actualLength];
  Array.Copy(originalArray, startIndex, copy, 0, actualLength);
  return copy;
}

In your example, the last two arrays in the loop would be {14,15} and {15}.