.net - Try-catch on PostgreSQL not catching exception -

i testing postgresql connection using npgsql . want know happens when make mistake ,for example wrong connection string ,database down .... etc. made simple program test npgsqlexceptions try statement not catching exception:

using system; using system.collections.generic; using system.componentmodel; using system.data; using system.drawing; using system.linq; using system.text; using system.threading.tasks; using system.windows.forms; using npgsql;  namespace windowsformsapplication1 {    public partial class form1 : form    {       public form1()       {          initializecomponent();       }        private void button1_click(object sender, eventargs e)       {      npgsqlconnection conn = new         npgsqlconnection("server=127.0.0.1;port=5432;user id=postgres;password=knbvbnv;database=testdb;");          try          {             conn.open();           }          catch (npgsqlexception ee)          {             console.writeline("========  ee.code  ===============");             console.writeline(ee.code);             console.writeline("========  ee.columnname  ===============");             console.writeline(ee.columnname);             console.writeline("========   ee.constraintname ===============");             console.writeline(ee.constraintname);             console.writeline("========  ee.datatypename  ===============");             console.writeline(ee.datatypename);             console.writeline("======== detail   ===============");             console.writeline(ee.detail);             console.writeline("========  errorcode  ===============");             console.writeline(ee.errorcode);             console.writeline("========  hresult  ===============");             console.writeline(ee.hresult);             console.writeline("======== internalquery   ===============");             console.writeline(ee.internalquery);             console.writeline("======== message   ===============");             console.writeline(ee.message);             console.writeline("========  messagetext  ===============");             console.writeline(ee.messagetext);             console.writeline("========  position  ===============");             console.writeline(ee.position);             console.writeline("========  severity  ===============");             console.writeline(ee.severity);             console.writeline("======== targetsite   ===============");             console.writeline(ee.targetsite);             console.writeline("========   ===============");             console.writeline(ee.where);             console.writeline("========    ===============");           }       }    } } 

how come try not catch errors ?

exception in visual studio : unhandled exception of type 'system.net.sockets.socketexception' occurred in npgsql.dll

additional information: no connection made because target machine actively refused it

it's throwing socketexception. you're catching npgsqlexception. if add secondary catch socketexception, it'll catch.