my use a 3 FileUpload, I am want one filupload was empty whe

As per your code you are tried to upload 3 files and save the file name in the DB. Hope that it you want to insert them into server. If yes, i have changed your code check it and let me know.

 string fileName1=string.Empty;
            string fileName2 = string.Empty;
            string fileName3 = string.Empty;
            if (FileUpload1.HasFile)
                fileName1 = Path.GetFileName(FileUpload1.FileName);
            if (FileUpload2.HasFile)
                fileName2 = Path.GetFileName(FileUpload2.FileName);
            if (FileUpload3.HasFile)
                fileName3 = Path.GetFileName(FileUpload3.FileName);

            if (!String.IsNullOrEmpty(fileName1) && FileUpload1.PostedFile != null)
            {

                FileUpload1.SaveAs(Server.MapPath("~/resource/Pembentukan/") + fileName1);

            }

            if (!String.IsNullOrEmpty(fileName2) && FileUpload2.PostedFile != null)
            {

                FileUpload2.SaveAs(Server.MapPath("~/resource/Pengelolaan/") + fileName2);

            }

            if (!String.IsNullOrEmpty(fileName2) && FileUpload3.PostedFile != null)
            {

                FileUpload3.SaveAs(Server.MapPath("~/resource/Retribusi/") + fileName3);

            }

            string Queryinsert = "INSERT INTO tbl_peraturan (propinsi_id,kabupaten_id,sektor_id,namafile1,namafile2,namafile3,perda_pembentukan,perda_pengelolaan,perda_retribusi)" +

            " VALUES(@propinsi_id,@kabupaten_id,@sektor_id,@namafile1,@namafile2,@namafile3,@perda_pembentukan,@perda_pengelolaan,@perda_retribusi)";

            using (MySqlConnection con = new MySqlConnection(strConnString))
            {

                using (MySqlCommand cmd = new MySqlCommand())
                {

                    cmd.Connection = con;

                    cmd.CommandType = CommandType.Text;

                    cmd.CommandText = Queryinsert;

                    cmd.Parameters.AddWithValue("@propinsi_id", cmbprovinsi.Text);

                    cmd.Parameters.AddWithValue("@kabupaten_id", cmbkabupaten.Text);

                    cmd.Parameters.AddWithValue("@sektor_id", cmbsektor.Text);

                    cmd.Parameters.AddWithValue("@namafile1", fileName1);

                    cmd.Parameters.AddWithValue("@namafile2", fileName2);

                    cmd.Parameters.AddWithValue("@namafile3", fileName3);

                    cmd.Parameters.AddWithValue("@perda_pembentukan", "resource/Pembentukan/" + fileName1);

                    cmd.Parameters.AddWithValue("@perda_pengelolaan", "resource/Pengelolaan/" + fileName2);

                    cmd.Parameters.AddWithValue("@perda_retribusi", "resource/Retribusi/" + fileName3);

                    try
                    {

                        con.Open();

                        cmd.ExecuteNonQuery();

                    }

                    catch (Exception ex)
                    {

                        lblerror.Text = "Data Tidak dapat Di Simpan.!!!" + ex;

                    }

                    finally
                    {

                        Response.Redirect(Request.Url.AbsoluteUri, true);

                        con.Close();

                        //

                    }

                }

            }