how to handle "argumentexception was unhandled by user" error in asp.net? -

protected void button2_click(object sender, eventargs e) {     using (sqlconnection con = new sqlconnection())     {         con.connectionstring = @"admin\localhost;initial catalog=maha;integrated security=true";         con.open();          sqlcommand cmd = new sqlcommand("insert dbo.student values ('" + tb1.text + "','" + tb2.text + "','" + tb3.text + "','" + @rm + "')", con);          cmd.executenonquery();         con.close();     } } 

the connection string wrong on admin\localhost , there come error message.

must like:

 con.connectionstring = @"data source=localhost;initial catalog=maha;integrated security=true"; 

beside must parameterize query , avoid sql injection https://stackoverflow.com/search?q=sql+injection

how sql injection "bobby tables" xkcd comic work?

and can read: setting connection string in asp.net sql server