c# - How to update multiple rows in a table without using a loop? -

i'm there must way this, executenonquery wouldn't exist if couldn't alter more 1 row @ time, can't figure out how. @ moment i'm updating values in customer table code:

            (int = 0; < datagridview1.rowcount; i++)         {              string connectionstring = @"data source = a103-17\sqlexpress17; initial catalog = carrental; integrated security = true";              string myupdate = "update [carrental].[dbo].[customer] " + //                "set [customerid] = @customerid, " +             "set [firstname] = @firstname, " +             "[lastname] = @lastname, " +             "[streetno] = @streetno, " +             "[streetname]= @streetname, " +             "[suburb] = @suburb, " +             "[state] = @state, " +             "[postcode] = @postcode, " +             "[mobphone] = @mobphone, " +             "[driverlicno] = @driverlicno, " +             "[creditcardtype] = @creditcardtype, " +             "[creditcardno] = @creditcardno, " +             "[expdate] = @expdate, " +             "[nameoncreditcard] = @nameoncreditcard " +             "where [customerid] = @customerid" +             ";";              sqlconnection con = new sqlconnection(connectionstring);             using (sqlcommand apptupdate = new sqlcommand(myupdate, con))             {                 apptupdate.parameters.addwithvalue("@customerid", datagridview1.rows[i].cells["customerid"].value ?? dbnull.value);                 apptupdate.parameters.addwithvalue("@firstname", datagridview1.rows[i].cells["firstname"].value ?? "null");                 apptupdate.parameters.addwithvalue("@lastname", datagridview1.rows[i].cells["lastname"].value ?? "null");                 apptupdate.parameters.addwithvalue("@streetno", datagridview1.rows[i].cells["streetno"].value ?? "null");                 apptupdate.parameters.addwithvalue("@streetname", datagridview1.rows[i].cells["streetname"].value ?? "null");                 apptupdate.parameters.addwithvalue("@suburb", datagridview1.rows[i].cells["suburb"].value ?? "null");                 apptupdate.parameters.addwithvalue("@state", datagridview1.rows[i].cells["state"].value ?? "null");                 apptupdate.parameters.addwithvalue("@postcode", datagridview1.rows[i].cells["postcode"].value ?? "null");                 apptupdate.parameters.addwithvalue("@mobphone", datagridview1.rows[i].cells["mobphone"].value ?? "null");                 apptupdate.parameters.addwithvalue("@driverlicno", datagridview1.rows[i].cells["driverlicno"].value ?? "null");                 apptupdate.parameters.addwithvalue("@creditcardtype", datagridview1.rows[i].cells["creditcardtype"].value ?? "null");                 apptupdate.parameters.addwithvalue("@creditcardno", datagridview1.rows[i].cells["creditcardno"].value ?? "null");                 apptupdate.parameters.addwithvalue("@expdate", datagridview1.rows[i].cells["expdate"].value ?? datetime.now);                 apptupdate.parameters.addwithvalue("@nameoncreditcard", datagridview1.rows[i].cells["nameoncreditcard"].value ?? "null");                  con.open();                 messagebox.show(apptupdate.executenonquery().tostring());                 con.close();             };         }      } 

this works, messagebox pop showing value of 1 each row, rather once showing value corresponding how many rows changed. can't move execution outside of loop, can't figure out how use out of rows affected return of executenonquery. how can use feature correctly?

combine customerid's comma separated string first. instead of where customerid = @customerid use where customerid in (@customerids)

@customerids string