ODP.NET连接异常

首先，我想说的是，我对Oracle数据库一点都不熟悉，所以我的措辞可能选择不当，我对某些概念的理解可能是错误的。。。无论如何，我正在尝试使用ODP.NET连接到Oracle 11g数据库，每次它都会给我这个异常：

System.TypeInitializationException occurred
HResult=-2146233036
Message=The type initializer for 'OracleInternal.Network.AddressResolution' threw an exception.
Source=Kiwi.ServiceBase
TypeName=OracleInternal.Network.AddressResolution
StackTrace:
    at OracleInternal.ConnectionPool.PoolManager`3.CreateNewPR(Int32 reqCount, Boolean bForPoolPopulation, ConnectionString csWithDiffOrNewPwd, String instanceName)
    at OracleInternal.ConnectionPool.PoolManager`3.Get(ConnectionString csWithDiffOrNewPwd, Boolean bGetForApp, String affinityInstanceName, Boolean bForceMatch)
    at OracleInternal.ConnectionPool.OraclePoolManager.Get(ConnectionString csWithNewPassword, Boolean bGetForApp, String affinityInstanceName, Boolean bForceMatch)
    at OracleInternal.ConnectionPool.OracleConnectionDispenser`3.Get(ConnectionString cs, PM conPM, ConnectionString pmCS, SecureString securedPassword, SecureString securedProxyPassword)
    at Oracle.ManagedDataAccess.Client.OracleConnection.Open()
    at Kiwi.DataAccess.OracleDataService.get_DbConnection() in c:'Projects'Kiwi-Beta7-0'Kiwiweb'src'Common'ApplicationServices'DataService'OracleDataService.cs:line 28
    InnerException: System.TypeInitializationException
        HResult=-2146233036
        Message=The type initializer for 'OracleInternal.Network.LDAP' threw an exception.
        Source=Oracle.ManagedDataAccess
        TypeName=OracleInternal.Network.LDAP
        StackTrace:
            at OracleInternal.Network.LDAP..ctor()
            at OracleInternal.Network.AddressResolution..cctor()
        InnerException: System.NullReferenceException
            HResult=-2147467261
            Message=Object reference not set to an instance of an object.
            Source=Oracle.ManagedDataAccess
            StackTrace:
                at OracleInternal.Network.LDAP._LDAP(Hashtable dsMap)
                at OracleInternal.Network.LDAP..cctor()
            InnerException:

调用方：

private System.Data.IDbConnection _dbConnection;
public override IDbConnection DbConnection
{
    get
    {
        if (_dbConnection.State == ConnectionState.Closed)
            _dbConnection.Open();        // Crash from HERE
        return _dbConnection;
    }
}

编辑其他信息：我也试图在没有tnsname.ora文件的情况下进行连接。这是在数据库所在的同一服务器上运行的windows服务。

我尝试了以下连接字符串，第一个在调试中工作（也是由应用程序构建的）：

Data Source=demosyr20140329:1521/demosyr;User ID=SEI;password=manager;Pooling = False;
Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)       (HOST=DEMOSYR20140329)(PORT=1521))(CONNECT_DATA=(SID=DEMOSYR)));User Id=system;Password=manager;
Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=DEMOSYR20140329)(PORT=1521)))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=DEMOSYR)));
Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=DEMOSYR20140329)(PORT=1521))(CONNECT_DATA=(SID=DEMOSYR)));  User Id=system;Password=manager;
User Id=system;Password=manager;Data Source=oracle
Data Source=system/manager@//DEMOSYR20140329:1521/DEMOSYR;

知道吗？