c# - how to declare the scalar variable "@CIN" in this code -

    private void button2_click(object sender, eventargs e)     {          // open connection using connection string.         sqlconnection con = new sqlconnection(@"data source=win-6q836p8jq1c\oby;initial catalog=etudiant;integrated security=true");         con.open();         string sqlquery = "insert abscence (cin,heure_debut,heure_fin,date)";         sqlquery += "values ('cin', 'heure_debut', 'heure_fin', 'date')";             // insert sql table. executenonquery best inserts.             using (sqlcommand com = new sqlcommand(sqlquery, con))             {                 (int = 0; < datagridview1.rows.count; i++)                 {                     com.parameters.addwithvalue("cin", datagridview1.rows[i].cells["cin"].value);                     com.parameters.addwithvalue("heure_debut", datagridview1.rows[i].cells["column1"].value);                     com.parameters.addwithvalue("heure_fin",datagridview1.rows[i].cells["column2"].value);                     com.parameters.addwithvalue("date", datetimepicker1.text);                    }                 com.executenonquery();                 com.parameters.clear();                 con.close();             }         }     } 

please me it's baccalaureate project

first in query don't have parameters, there no need write query concatanation of 2 strings:

string sqlquery = @"insert                         abscence (cin,heure_debut,heure_fin,date)                     values                        (@cin, @heure_debut, @heure_fin, @date)"; 

you can write string on more 1 line using symbol @, before starting string @"".

to declare parameter again using @ symbol. when add them value should written this:

com.parameters.addwithvalue("@cin", datagridview1.rows[i].cells["cin"].value); com.parameters.addwithvalue("@heure_debut",datagridview1.rows[i].cells["column1"].value); com.parameters.addwithvalue("@heure_fin",datagridview1.rows[i].cells["column2"].value); com.parameters.addwithvalue("@date", datetimepicker1.text);