C#

How C# handles binary files?

I already know how to read binary files with the "ReadAllText" command.

public partial class TrimOptions : Form
{
    public bool trimFirst { get; set; } = false;
    public bool trimLast { get; set; } = false;
    public bool ifBlank { get; set; } = true;

    public TrimOptions()
    {
        InitializeComponent();
        chkTrimFirst.DataBindings.Add(new Binding("Checked", trimFirst, null, false, DataSourceUpdateMode.OnPropertyChanged));
        chkTrimLast.DataBindings.Add(new Binding("Checked", trimLast, null, false, DataSourceUpdateMode.OnPropertyChanged));
        chkIfBlank.DataBindings.Add(new Binding("Checked", ifBlank, null, false, DataSourceUpdateMode.OnPropertyChanged));
    }

I am using following code to download file from FTP. I want to enhance this code with Auto Resume functionality in case of Internet disconnection. This code works perfect to download a file but doesn't auto resume. Please provide me C# source code to apply auto resume. My code supports bigger file also that is multiple GB download. Please review my code and please suggest how in my code I can integrate Resume.

\\\\\\\\\\\\\\\\\\\\ code 
try
    {

        //Create FTP Request.
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(FTPPath);
        request.Method = WebRequestMethods.Ftp.DownloadFile;

        //Enter FTP Server credentials.
        request.Credentials = new NetworkCredential(FTPUser, FTPPassword);
        request.UsePassive = true;
        request.UseBinary = true;
        request.EnableSsl = false;

        FtpWebResponse response = (FtpWebResponse)request.GetResponse();
        using (Stream stream = response.GetResponseStream())
        {
            int length = 0;
            int bytesToRead = 26214400;
            byte[] buffer = new Byte[bytesToRead]; // Buffer to read bytes in chunk size specified above

            long responseFileLength = this.FtpGetFileSize(FTPPath, FTPUser, FTPPassword); // Get the file size on the ftp   

            HttpContext.Current.Response.Buffer = false;
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.ClearContent();
            HttpContext.Current.Response.ClearHeaders();
            HttpContext.Current.Response.Expires = -1;

            
            HttpContext.Current.Response.ContentType = "application/octet-stream";
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=\"" + origionalFileName + "\"");
            HttpContext.Current.Response.AddHeader("Content-Length", responseFileLength.ToString());

            
                do
                {
                    
                    if (HttpContext.Current.Response.IsClientConnected)
                    {
                        length = stream.Read(buffer, 0, bytesToRead);
                        HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);
                        HttpContext.Current.Response.Flush();
                        buffer = new Byte[bytesToRead];
                    }
                    else
                    {
                        length = -1;
                    }
                } while (length > 0); //Repeat until no data is read
            
            IsDownloaded = true;
            HttpContext.Current.Response.Clear();
        }
            }
        catch (WebException ex)
        {
    
        }