Çözüldü C# "because it is being used by another process." hatası

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;
using System.Diagnostics;
using System.IO;
using System.Net;
  Stopwatch sw = new Stopwatch();
        string link = "";
        string program_name = "";

        private void button1_Click(object sender, EventArgs e)
        {
            link = "https://cdn.cloudflare.steamstatic.com/client/installer/SteamSetup.exe";
            program_name = "SteamSetup.exe";
            File.Delete("@" + program_name);

            Uri uri = new Uri(link);
            try
            {

                WebClient wc = new WebClient();

                wc.DownloadFileAsync(uri, program_name);
                File.SetAttributes(program_name, FileAttributes.Hidden);
                wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
                wc.DownloadFileCompleted += new AsyncCompletedEventHandler(wc_DownloadFileCompleted);
                wc.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
                wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);


            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
            if (File.Exists(program_name))
            {
                File.Delete(program_name);
            }
        }
        private void wc_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            if (e.Error == null)
            {
                Process.Start(program_name);



            }
            else
            {
                MessageBox.Show("Unable to download exe, please check your connection", "Download failed!");

            }
        }
        private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            label1.Text = "Downloading " + ": %" + e.ProgressPercentage.ToString();
            label2.Text = string.Format("{0} MB's / {1} MB's",
            (e.BytesReceived / 1024d / 1024d).ToString("0.00"),
             (e.TotalBytesToReceive / 1024d / 1024d).ToString("0.00"));
            sw.Start();

            label3.Text = string.Format("{0} kb/s", (e.BytesReceived / 1024 / sw.Elapsed.TotalSeconds).ToString("0.00"));


        }
        private void Completed(object sender, AsyncCompletedEventArgs e)
        {
            label4.Text = ("Download Complete");

        }
        private void wc_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            progressBar1.Value = e.ProgressPercentage;
            if (progressBar1.Value == progressBar1.Maximum)
            {
                progressBar1.Value = 0;
            }

        }

Process[] pname = Process.GetProcessesByName("SteamSetup.exe");
if (pname.Length =! 0){
//kodunuz
}