title: Why i get ORA-12504 error in my connection string?
body: <p>I'm beginner in oracle,want to connect oracle database with c# windows appliation<br/>
  but why i try connect database i get this error:<br/>
  <a href="https://i.stack.imgur.com/dkTl3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dkTl3.png" alt="enter image description here"></a></p>
  
  <p><br/>
  my listener file is this:<br/></p>
  
  <pre><code>MYLISTNER =
    (DESCRIPTION_LIST =
      (DESCRIPTION =
        (ADDRESS = (PROTOCOL = TCP)(HOST = DESKTOP-A5CFJSH)(PORT = 1521))
        (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      )
    )
  
  SID_LIST_MYLISTNER =
    (SID_LIST =
      (SID_DESC =
        (SID_NAME = CLRExtProc)
        (ORACLE_HOME = C:\app\BEHZAD-HUSH\product\11.2.0\dbhome_2)
        (PROGRAM = extproc)
        (ENVS = "EXTPROC_DLLS=ONLY:C:\app\BEHZAD-HUSH\product\11.2.0\dbhome_2\bin\oraclr11.dll")
      )
    )
  
  ADR_BASE_MYLISTNER = C:\app\BEHZAD-HUSH
  </code></pre>
  
  <p><br/>
  and my tnsnames file is:<br/></p>
  
  <pre><code>ORACLR_CONNECTION_DATA =
    (DESCRIPTION =
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      )
      (CONNECT_DATA =
        (SID = CLRExtProc)
        (PRESENTATION = RO)
      )
    )
  </code></pre>
  
  <p><br/>
  What happen?How can i solve that?thanks.</p>
  
  <p><br/>
  my tns ping is:<br/></p>
  
  <pre><code>TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 02-NOV-2015 15:42:22
  
  Copyright (c) 1997, 2010, Oracle.  All rights reserved.
  
  Used parameter files:
  C:\app\BEHZAD-HUSH\product\11.2.0\dbhome_2\network\admin\sqlnet.ora
  
  
  Used TNSNAMES adapter to resolve the alias
  Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))) (CONNECT_DATA = (SID = CLRExtProc) (PRESENTATION = RO)))
  TNS-12541: TNS:no listener
  </code></pre>