C# - Access denied when using AppDomain.CurrentDomain.BaseDirectory

I have created an application that has an update system, something unconventional:

this app is installed and run from:

C:\Program Files (x86)\Application test

the executable is called:

searchdata.exe

but at some point I had the great idea to make an update system that executes the following steps:

1. Click the update button: check if the executable exists update.exe.

• if it exists, run it immediately and close searchdata.exe.
• does not exist - download update.datfrom a URL and rename it to update.exe.

2. This is the download and progress bar script:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            DownloadFileWithProgress("http://test.pro/installer/update.dat", AppDomain.CurrentDomain.BaseDirectory + "update.exe", ProgressBar1, Label4);
        }

        private void DownloadFileWithProgress(string DownloadLink, string TargetPath, ProgressBar Progress, Label LabelProgress)
        {
            int bytesProcessed = 0;
            Stream remoteStream = null;
            Stream localStream = null;
            HttpWebResponse response = null;
            try
            {
                WebRequest request = WebRequest.Create(DownloadLink);
                double TotalBytesToReceive = 0;
                var SizewebRequest = WebRequest.Create(new Uri(DownloadLink));
                SizewebRequest.Method = "HEAD";
                using (var WebResponse = SizewebRequest.GetResponse())
                {
                    var fileSize = WebResponse.Headers.Get("Content-Length");
                    TotalBytesToReceive = Convert.ToDouble(fileSize);
                }
                response = (HttpWebResponse)request.GetResponse();
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    remoteStream = response.GetResponseStream();
                    string filePath = TargetPath;
                    localStream = File.Create(filePath); // Aquí mero es el error
                    byte[] buffer = new byte[1024];
                    int bytesRead = 0;
                    do
                    {
                        bytesRead = remoteStream.Read(buffer, 0, buffer.Length);
                        localStream.Write(buffer, 0, bytesRead);
                        bytesProcessed += bytesRead;
                        double bytesIn = double.Parse(bytesProcessed.ToString());
                        double percentage = bytesIn / TotalBytesToReceive * 100;
                        percentage = Math.Round(percentage, 0);
                        if (Progress.InvokeRequired)
                        {
                            Progress.Invoke(new MethodInvoker(() =>
                            {
                                Progress.Value = int.Parse(Math.Truncate(percentage).ToString());
                            }));
                        }
                        else
                        {
                            Progress.Value = int.Parse(Math.Truncate(percentage).ToString());
                        }
                        if (LabelProgress.InvokeRequired)
                        {
                            LabelProgress.Invoke(new MethodInvoker(() =>
                            {
                                LabelProgress.Text = int.Parse(Math.Truncate(percentage).ToString()) + "%";
                            }));
                        }
                        else
                        {
                            LabelProgress.Text = int.Parse(Math.Truncate(percentage).ToString()).ToString() + "%";
                        }
                    }
                    while (bytesRead > 0);
                }
                else
                {
                    throw new ArgumentException(response.StatusDescription, "Respuesta del Servidor");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error en DownloadFileWithProgress" + ex.Message);
            }
            finally
            {
                if (response != null)
                    response.Close();
                if (remoteStream != null)
                    remoteStream.Close();
                if (localStream != null)
                    localStream.Close();
            }
        }

3. the problem is that I'm running with normal privileges, I don't want to have to use administrative privileges , but running gives me an access denied error when trying to write the file to the application directory.