How to copy part of an array to another array in C#?

See this question. LINQ Take() and Skip() are the most popular answers, as well as Array.CopyTo().

A purportedly faster extension method is described here.

int[] a = {1,2,3,4,5};

int [] b= new int[a.length]; //New Array and the size of a which is 4

Array.Copy(a,b,a.length);

Where Array is class having method Copy, which copies the element of a array to b array.

While copying from one array to another array, you have to provide same data type to another array of which you are copying.

In C# 8+ you can use ranges.

int a[] = {1,2,3,4,5};
int b[] = a[1..4]; // b = [2,3,4];

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-8.0/ranges

Note: I found this question looking for one of the steps in the answer to how to resize an existing array.

So I thought I would add that information here, in case anyone else was searching for how to do a ranged copy as a partial answer to the question of resizing an array.

For anyone else finding this question looking for the same thing I was, it is very simple:

Array.Resize<T>(ref arrayVariable, newSize);

where T is the type, i.e. where arrayVariable is declared:

T[] arrayVariable;

That method handles null checks, as well as newSize==oldSize having no effect, and of course silently handles the case where one of the arrays is longer than the other.

See the MSDN article for more.

In case if you want to implement your own Array.Copy method.

Static method which is of generic type.

 static void MyCopy<T>(T[] sourceArray, long sourceIndex, T[] destinationArray, long destinationIndex, long copyNoOfElements)
 {
  long totaltraversal = sourceIndex + copyNoOfElements;
  long sourceArrayLength = sourceArray.Length;

  //to check all array's length and its indices properties before copying
  CheckBoundaries(sourceArray, sourceIndex, destinationArray, copyNoOfElements, sourceArrayLength);
   for (long i = sourceIndex; i < totaltraversal; i++)
     {
      destinationArray[destinationIndex++] = sourceArray[i]; 
     } 
  }

Boundary method implementation.

private static void CheckBoundaries<T>(T[] sourceArray, long sourceIndex, T[] destinationArray, long copyNoOfElements, long sourceArrayLength)
        {
            if (sourceIndex >= sourceArray.Length)
            {
                throw new IndexOutOfRangeException();
            }
            if (copyNoOfElements > sourceArrayLength)
            {
                throw new IndexOutOfRangeException();
            }
            if (destinationArray.Length < copyNoOfElements)
            {
                throw new IndexOutOfRangeException();
            }
        }