Creating Visual Web part for file upload

I am trying to create a visual web part to upload documetns using FileUpload control. Below is the working code for uploading a file.

    protected void UploadButton_Click(object sender, EventArgs e)
        {
            string DocumentLibName = "Shared Documents";

            SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                using (SPSite objsite = new SPSite("http://demo:13121/VisualWebParts/"))
                {
                    using (SPWeb objWeb = objsite.OpenWeb())
                    {
                        objWeb.AllowUnsafeUpdates = true;           
                        Boolean replaceExistingFiles = true;
                        if (FileUploadControl.PostedFile != null)
                        {
                            Stream fStream = FileUploadControl.PostedFile.InputStream;
                            byte[] contents = new byte[fStream.Length];
                            fStream.Read(contents, 0, (int)fStream.Length);
                            fStream.Close();
                            string Filename = FileUploadControl.FileName;
                            string destUrl = SPContext.Current.Web.Url + "/" + DocumentLibName + "/" + Filename;
                            objWeb.Files.Add(destUrl, contents, replaceExistingFiles);

                        }
                        else {
}                        
                        objWeb.AllowUnsafeUpdates = false;
                    }
                }
            });                            
        }

Now I need to upload files to list in the attachment column. It doesnt work when I replace the DocumentLibName as the list name. It gives an error that the There is no file with URL "https://xyz/"