c# - sqlconnection missing type or namespace reference -

i have sql query want use results database. when try open sqlconnection, code won't compile , error asking if missing using directive.

using system; using system.collections.generic; using system.linq; using system.web; using system.web.ui; using system.web.ui.webcontrols; using system.io; using system.data; using system.data.sql; using system.data.sqlclient; using system.configuration; using system.collections;   namespace hackoffice.superadmin {     public partial class foundusbreakdown : system.web.ui.page     {         protected void page_load(object sender, eventargs e)         {             grabdata();         }         private void grabdata()         {             string chartdataquery = "select accounttype, count(*) entries hackoffice.dbo.onlinesignups group accounttype";             using (sqlconnection connection = new sqlconnection(connectionstring));         }     } } 

i'm confused because have same using directives on other pages , not getting same error on pages.

class names case sensitive in c#. need sqlconnection, not sqlconnection.

also, you're creating empty using statement dispose resource immediately. when open using block, you'll want put code uses idisposable resource inside block:

using (sqlconnection connection = new sqlconnection(connectionstring)) {    // code uses sqlconnection goes inside block. }