Hi nauna,

Check with below code.

C#

protected string UploadFolderPath = "http://mycherry2.msonlinegroup.com/DynamicImage/";
protected void OnUploadComplete(object sender, AjaxFileUploadEventArgs e)
{
    UploadFolderPath = UploadImages(e);
}
public string UploadImages(AjaxFileUploadEventArgs e)
{
    string uploadFileName = "";
    if (!string.IsNullOrEmpty(e.FileName))
    {
        ext = Path.GetExtension(e.FileName).ToLower();
        if (ext == ".jpg" || ext == ".jpeg" || ext == ".gif" || ext == ".png")
        {
            uploadFileName = System.IO.Path.GetFileName(e.FileName);
        }
        string ftp = ftppath;
        string ftpFolder = domainname + "/DynamicImage/" + uploadFileName;

        byte[] fileBytes = null;
        string fileName = Path.GetFileName(uploadFileName);
        using (Stream fs = e.GetStreamContents())
        {
            using (BinaryReader br = new BinaryReader(fs))
            {
                fileBytes = br.ReadBytes((Int32)fs.Length);
            }
        }
        try
        {
            FtpWebRequest request = (FtpWebRequest)WebRequest.Create(ftp + ftpFolder);
            request.Method = WebRequestMethods.Ftp.UploadFile;
            request.Credentials = new NetworkCredential(username, password);
            request.ContentLength = fileBytes.Length;
            request.UsePassive = true;
            request.UseBinary = true;
            request.ServicePoint.ConnectionLimit = fileBytes.Length;
            request.EnableSsl = false;
            using (Stream requestStream = request.GetRequestStream())
            {
                requestStream.Write(fileBytes, 0, fileBytes.Length);
                requestStream.Close();
            }
            FtpWebResponse response = (FtpWebResponse)request.GetResponse();
            path = returnpath + "/DynamicImage/" + uploadFileName;

            response.Close();
        }
        catch (WebException ex)
        {
            throw new Exception((ex.Response as FtpWebResponse).StatusDescription);
        }
    }
    HttpContext.Current.Session["Path"] = path;

    return path;
}