protected void upload_document_Click(object sender, EventArgs e)
    {
        try
        {
            if (!DocumentUploader.HasFile)
                throw new Exception("Please provide a file.");

            long convertedStudentId;
            if (!Int64.TryParse(Session["userid"].ToString(), out convertedStudentId))
                throw new Exception("Cannot find user ID, please contact administrator.");

            string filename = DocumentUploader.FileName;
            FileModule fileModule = new FileModule();
            ProjectDocument projectDocument = fileModule.saveProjectFile(DocumentUploader.PostedFile.InputStream, FILE_TYPE.DOCUMENT,filename);
            uploaded_document_info.Text = filename;

            //store ID in hidden_uploaded_doc_ID
            hidden_uploaded_doc_ID.Value = projectDocument.PROJECTFILE_ID.ToString();

            Messenger.setMessage(error_message, "File uploaded successfully.", LEVEL.SUCCESS);
            //refreshCategoryList();
        }
        catch (SaveFileException sfex)
        {
            Messenger.setMessage(error_message, sfex.Message, LEVEL.DANGER);
        }
        catch (Exception ex)
        {
            Messenger.setMessage(error_message, ex.Message, LEVEL.DANGER);
        }
        finally
        {
            error_modal_control.Show();
            //NewProjectUpdatePanel.Update();
            selected_categories.Value = "";
        }
    }