Question

If not what’s the best way to create it ?

Note: merging is not just appending, it fusionned keys that are the same.

Answer 1

This functionality exist on a List element. Arrays are fixed width items in C#, so you can’t modify the size without creating a new array. However, Lists are a different story. You can do:

List<int> sample = oldList.AddRange(someOtherList);
// sample contains oldList with all elements of someOtherList appended to it.

Additionally, with LINQ it’s trivially easy to convert between List and Array with the

.ToList()
.ToArray()

extension methods. If you want to do that with an indeterminate number of arrays, you could do something like this:

public static class ArrayExtensions
{
     public static T[] MergeArrays<T>(this T[] sourceArray, params T[][] additionalArrays)
     {
          List<int> elements = sourceArray.ToList();

          if(additionalArrays != null)
          {
               foreach(var array in additionalArrays)
                   elements.AddRange(array.ToList());
          }

          return elements.ToArray();
     }
}

And call:

int[] mergedArray = initialArray.MergeArrays(array1, array2, array3 /* etc */);