Invalid URI: the URI is empty.

Hello

I want to read address lines from a file. I do not a user to enter URLs.

I wrote this: (Now I do not have this Error: cross-thread operation not valid: control 'txtUrl' accessed from a thread other than the thread it was created on)

                    String FilePath_address = Application.StartupPath + @"\address.txt";
                    string line = "";
                    // Read the file and display it line by line.
                    System.IO.StreamReader file = new System.IO.StreamReader(FilePath_address);
                    while ((line = file.ReadLine()) != null)
                    {
                        if (txtUrl.InvokeRequired)
                        {
                            txtUrl.Invoke(new MethodInvoker(delegate { line = txtUrl.Text; }));
                        }
                        //txtUrl.Text = line;
                        //counter++;
                        //}
                        // Create a request to the file we are downloading
                        webRequest = (HttpWebRequest)WebRequest.Create(txtUrl.Text);

Now I have this Error:

Invalid URI: the URI is empty.