Writing code to UI in a separate thread slowing down function. C#

Question

I have some code below that goes through all the directories of a given area sDir it also runs on it's own thread. This builds a liststring that then gets converted to an array to build a treeview.

However I would also like to count the number of directories and files that the search is up to and display it on my UI. If i add the this.Invoke((MethodInvoker)(() => DirCL.Text = "Dir: " + dirC.ToString()));

and the this.Invoke((MethodInvoker)(() => FileCL.Text = "Files: " + FileC.ToString())); liststring.Add(Files);

This makes the function go from 10 seconds to do an area with 65,000 files to 100ish seconds.

I assume this Increase is because the MethodInvoker is pausing the function to go write to the UI.

Is there a better way for me to be writing code to the UI that is in a different thread?

int dirC = 0;
int FileC = 0;

private void DirSearch(string sDir)
        {
            try
            {
                string[] array1 = Directory.GetDirectories(sDir);
                for (int i1 = 0; i1 < array1.Length; i1++)
                {
                    string Dir = array1[i1];
                    dirC++;
                    //this.Invoke((MethodInvoker)(() => DirCL.Text = "Dir: " + dirC.ToString()));
                    try
                    {
                        String[] array = Directory.GetFiles(Dir, txtFile.Text);
                        for (int i = 0; i < array.Length; i++)
                        {
                            string Files = array[i];
                            FileC++;
                            //this.Invoke((MethodInvoker)(() => FileCL.Text = "Files: " + FileC.ToString()));
                            liststring.Add(Files);

                        }
                    }
                    catch (System.Exception excpt)
                    {
                        Console.WriteLine(excpt.Message);
                    }
                    DirSearch(Dir);
                }
            }
            catch (System.Exception excpt)
            {
                Console.WriteLine(excpt.Message);
                ErrC++;
            }

        }