.net - Error Help: There is already an open DataReader associated with this Command which must be closed first. -

i'm having error in part of code , i'm still unable figure out solution it

error stats:

executereader requires open , available connection. connection's current state open.

with source code in:

line 144: .commandtype = commandtype.text

line 145: .connection = cn

line 146: dr = .executereader

line 147: end

line 148:

the code is:

 public function getdbfield(byval query string, byval field string) string      'abriendo la conexion la base de datos      sqlconnect()      dim cmd new sqlcommand     dim result string = ""      dim dr sqldatareader     dr = nothing      'ejecutando el lector de     try          cmd             .commandtext = query             .commandtype = commandtype.text             .connection = cn             dr = .executereader         end        catch ex sqlexception         showalertmessage(ex.message)         getdbfield = nothing         exit function     end try      'escribiendo en una variable de texto     try         if dr.hasrows          end if         while dr.read             if isdbnull(dr(field).tostring) = true                 result = nothing             else                 result = dr(field).tostring             end if         end while     catch ex sqlexception         showalertmessage(ex.message)         getdbfield = nothing         exit function      end try      'cerrando la conexion de bd     sqldisconnect()      getdbfield = result end function 

really in need of kind of help

in replay last question code in vb page in app_code

#region "   variables globales"     public db string = "repuestosdr"      'public cnstr string = "driver={sql server native client 10.0};server=localhost;database=" & db & ";uid=crivera;pwd=crivera;"     public cnstr string = configurationmanager.connectionstrings("suoodconnection").connectionstring    '"driver={sql server};server=repuestosdr.db.10580944.hostedresource.com;database=" & db & ";uid=" & db & ";pwd=r34llyh4rd!;port=1433;"      public logged boolean = false      public qry string     public msg new msgboxresult       public ds new dataset     public dt new datatable     public dr sqldatareader     public cn new sqlconnection()     public da new sqldataadapter     public cmd sqlcommand   #end region 

for connection:

#region "   connection"     public function sqlconnect(optional byval mypage page = nothing) boolean         try             if cn.state = connectionstate.closed                 cn                     .connectionstring = cnstr                     .open()                 end             end if          catch myerror exception             showalertmessage("error connecting database" & chr(13) & myerror.message)             sqlconnect = false         end try         sqlconnect = true     end function