I'm trying to merge 3 arrays into one, what should I do?

Question

C++ / C#

Program code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Programm
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }
        string[] files =

        string[] convert(object sender, EventArgs e)
        {
            string[] files1 = Directory.GetFiles($"{Directory.GetCurrentDirectory()}media", "*.jpg", SearchOption.AllDirectories);
            string[] files2 = Directory.GetFiles($"{Directory.GetCurrentDirectory()}media", "*.png", SearchOption.AllDirectories);
            string[] files3 = Directory.GetFiles($"{Directory.GetCurrentDirectory()}media", "*.jpeg", SearchOption.AllDirectories);
            string[] files12 = files1.Concat(files2).ToArray();
            string[] files = files12.Concat(files3).ToArray();
            return files;
        }

I need to set the string[] files variable to the value of three concatenated arrays in the string[] convert function, but I get errors when calling the function and don't know what to do.

Answer 1

As an example

string[] convert() {
  string[] files = Directory.GetFiles(Environment.CurrentDirectory + @"\media", "*.jpg", SearchOption.AllDirectories);
  string[] files2 = Directory.GetFiles(Environment.CurrentDirectory + @"\media", "*.png", SearchOption.AllDirectories);
  string[] files3 = Directory.GetFiles(Environment.CurrentDirectory + @"\media", "*.jpeg", SearchOption.AllDirectories);
  string[] filesAll = new string[files.Length + files2.Length + files3.Length];
  files.CopyTo(filesAll, 0);
  files2.CopyTo(filesAll, files.Length);
  files3.CopyTo(filesAll, files.Length + files2.Length);
  return filesAll;
}