sql server - Conn.Open() still work after SQL Service is stopped -

i have met issue sql server 2005 sp2, have created windows form , button on it, , following steps:

1. make sure sql service running, click button, ok
2. stop sql service, , click button again, on machine, there not exception @ code of line 1, exception occurred @ line 2, , exception info:

message: transport-level error has occurred when sending request server. (provider: shared memory provider, error: 0 - no process on other end of pipe.)

using system; using system.collections.generic; using system.componentmodel; using system.data; using system.drawing; using system.text; using system.windows.forms; using system.data.sqlclient;  namespace reconnectsql {     public partial class form1 : form     {          private string m_connectionstring = @"server=(local); database=testdb; user id=sa; password=admins; connection timeout=15";          public form1()         {             initializecomponent();         }          /// <summary>         ///          /// </summary>         public datatable getbyfilldatatable()         {             try             {                 sqlcommand cmd = new sqlcommand("getalldata");                 cmd.commandtype = commandtype.storedprocedure;                  datatable dt = this.getdatatable(cmd);                 return dt;             }             catch             {                 throw;             }         }           #region common funcs         /// <summary>         ///          /// </summary>         /// <param name="cmd"></param>         /// <returns></returns>         private datatable getdatatable(sqlcommand cmd)         {             datatable dt = new datatable();              using (sqlconnection conn = new sqlconnection(this.m_connectionstring))             {                 try                 {                     conn.open();  // line 1                 }                 catch (exception ex)                 {                     throw;                 }                  using (sqldataadapter adapter = new sqldataadapter())                 {                     try                     {                         cmd.connection = conn;                         cmd.commandtimeout = conn.connectiontimeout;                         adapter.selectcommand = cmd;                         adapter.fill(dt);  // line 2                     }                     catch (exception ex)                     {                         throw;                     }                 }             }              return dt;         }          #endregion                 private void button2_click(object sender, eventargs e)         {              try             {                 datatable dt = getbyfilldatatable();                 listbox1.items.add("getbyfilldatatable called without exceptions!");             }             catch (exception ex)             {                 listbox1.items.add(ex.message);             }            }     } } 

detailed exception info:

-       [system.data.sqlclient.sqlexception]    {"a transport-level error has occurred when sending request server. (provider: shared memory provider, error: 0 - no process on other end of pipe.)"} system.data.sqlclient.sqlexception +       base    {"a transport-level error has occurred when sending request server. (provider: shared memory provider, error: 0 - no process on other end of pipe.)"} system.data.common.dbexception {system.data.sqlclient.sqlexception}         class   20  byte +       errors  {system.data.sqlclient.sqlerrorcollection}  system.data.sqlclient.sqlerrorcollection         linenumber  0   int         number  233 int         procedure   null    string         server  "(local)"   string         source  ".net sqlclient data provider"  string         state   0   byte 

stacktrace

at system.data.sqlclient.sqlconnection.onerror(sqlexception exception, boolean breakconnection)    @ system.data.sqlclient.sqlinternalconnection.onerror(sqlexception exception, boolean breakconnection)    @ system.data.sqlclient.tdsparser.throwexceptionandwarning(tdsparserstateobject stateobj)    @ system.data.sqlclient.tdsparserstateobject.writesni()    @ system.data.sqlclient.tdsparserstateobject.writepacket(byte flushmode)    @ system.data.sqlclient.tdsparserstateobject.executeflush()    @ system.data.sqlclient.tdsparser.tdsexecuterpc(_sqlrpc[] rpcarray, int32 timeout, boolean inschema, sqlnotificationrequest notificationrequest, tdsparserstateobject stateobj, boolean iscommandproc)    @ system.data.sqlclient.sqlcommand.runexecutereadertds(commandbehavior cmdbehavior, runbehavior runbehavior, boolean returnstream, boolean async)    @ system.data.sqlclient.sqlcommand.runexecutereader(commandbehavior cmdbehavior, runbehavior runbehavior, boolean returnstream, string method, dbasyncresult result)    @ system.data.sqlclient.sqlcommand.runexecutereader(commandbehavior cmdbehavior, runbehavior runbehavior, boolean returnstream, string method)    @ system.data.sqlclient.sqlcommand.executereader(commandbehavior behavior, string method)    @ system.data.sqlclient.sqlcommand.executedbdatareader(commandbehavior behavior)    @ system.data.common.dbcommand.system.data.idbcommand.executereader(commandbehavior behavior)    @ system.data.common.dbdataadapter.fillinternal(dataset dataset, datatable[] datatables, int32 startrecord, int32 maxrecords, string srctable, idbcommand command, commandbehavior behavior)    @ system.data.common.dbdataadapter.fill(datatable[] datatables, int32 startrecord, int32 maxrecords, idbcommand command, commandbehavior behavior)    @ system.data.common.dbdataadapter.fill(datatable datatable)    @ reconnectsql.form1.getdatatable(sqlcommand cmd) in e:\_public_\sqlfail\reconnectsql\reconnectsql\form1.cs:line 138 

after investigations, seems connection still exist in connection pool sql stopped, after sql started , calling conn.open() connection object pool should invalid, sqldataadapter.fill cause exception

http://social.msdn.microsoft.com/forums/en-us/adodotnetdataproviders/thread/99963999-a59b-4614-a1b9-869c6dff921e