public DataTable  ConnectOracle()
        {
            using (OracleConnection conn = new OracleConnection("User Id=test;Password=test;Data Source=127.0.0.1/orcl;"))
            {
                //conn.Open();
                try
                {
                    OracleDataAdapter adapter = new OracleDataAdapter("select * from T_Student", conn);
                    DataTable dt = new DataTable();
                    adapter.Fill(dt);
                    return dt;
                }
                catch (Exception ex)
                {
                    throw;
                }
            }
        }

[OracleException (0x80131938): ORA-12154: TNS:could not resolve the connect identifier specified
]
   System.Data.OracleClient.OracleException.Check(OciErrorHandle errorHandle, Int32 rc) +340444
   System.Data.OracleClient.OracleInternalConnection.OpenOnLocalTransaction(String userName, String password, String serverName, Boolean integratedSecurity, Boolean unicode, Boolean omitOracleConnectionName) +881
   System.Data.OracleClient.OracleInternalConnection..ctor(OracleConnectionString connectionOptions) +129
   System.Data.OracleClient.OracleConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject) +40
   System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +31
   System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +548
   System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +69
   System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +470
   System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +108
   System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +118
   System.Data.OracleClient.OracleConnection.Open() +43
   System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +121
   System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) +160
   System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) +108
   WebFormDemo.Test.ConnectOracle() in D:\SourceCode\PracticeTest\WebFormDemo\Test.cs:27
   WebFormDemo.WebForm1.Page_Load(Object sender, EventArgs e) in D:\SourceCode\PracticeTest\WebFormDemo\WebForm1.aspx.cs:14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +51
   System.Web.UI.Control.OnLoad(EventArgs e) +92
   System.Web.UI.Control.LoadRecursive() +54
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +772