Affrontare il problema nel collegamento di Oracle con frameowrk di entità

Sto usando le versioni Oracle 11g e Entity Framework 6.

Sto affrontando il seguente errore:

"Si è verificato un errore durante il recupero delle informazioni del provider dal database, che può essere causato da Entity Framework che utilizza una stringa di connessione errata. Controlla le eccezioni interne per i dettagli e assicurati che la stringa di connessione sia corretta."

La mia app.config è la seguente:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework"
      type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/>

    <section name="oracle.manageddataaccess.client"
      type="OracleInternal.Common.ODPMSectionHandler, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342"/>
  </configSections>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
  </startup>
  <connectionStrings>
    <clear/>

    <add name="OracleDbContext" providerName="Oracle.ManagedDataAccess.Client"

      connectionString=" Data Source=HRFOLATEST1;User ID=hrms2;Password=hrms2;"/>

  </connectionStrings>
  <entityFramework>

    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework"/>

    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer"/>

      <provider invariantName="Oracle.ManagedDataAccess.Client"
        type="Oracle.ManagedDataAccess.EntityFramework.EFOracleProviderServices, Oracle.ManagedDataAccess.EntityFramework, Version=6.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342"/>

    </providers>

  </entityFramework>

  <system.data>

    <DbProviderFactories>

      <remove invariant="Oracle.ManagedDataAccess.Client"/>

      <add name="ODP.NET, Managed Driver" invariant="Oracle.ManagedDataAccess.Client" description="Oracle Data Provider for .NET, Managed Driver"

        type="Oracle.ManagedDataAccess.Client.OracleClientFactory, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342"/>

    </DbProviderFactories>

  </system.data>

  <runtime>

    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">

      <dependentAssembly>

        <publisherPolicy apply="no"/>

        <assemblyIdentity name="Oracle.ManagedDataAccess" publicKeyToken="89b483f429c47342" culture="neutral"/>

        <bindingRedirect oldVersion="4.121.0.0 - 4.65535.65535.65535" newVersion="4.121.2.0"/>

      </dependentAssembly>

    </assemblyBinding>

  </runtime>

</configuration>

Il mio contesto Db:

class DatabaseContext: DbContext

{
    public DatabaseContext() : base("OracleDbContext")
    {

    }
    public DbSet<User> Users { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Configure domain classes using modelBuilder here

        modelBuilder.Entity<User>().ToTable("HRMS_OLAS_TREE");

        modelBuilder.Entity<User>().Property(user => user.ID).HasColumnName("EMP_ID").HasColumnType("VARCHAR");

        modelBuilder.Entity<User>().Property(user => user.NAME).HasColumnName("EMP_NAME").HasColumnType("VARCHAR");

        base.OnModelCreating(modelBuilder);

    }
}

internal class User
{
    public long ID { get; set; }
    public string NAME { get; set; }

}

Per favore, lasciami ora quale errore sto facendo.