Thank you for the explanation. Machine.config does not contain appropriate DbProviderFactory, Oracle XE does not insert it into Machine.config. Hence I have edited LLBLGenPro.exe.config, here are some "interesting" parts of it:
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<!-- separate assembly paths. These are hints to help fusion when it gets confused. -->
<probing privatePath="SqlServerUDTAssemblies;Drivers\Oracle;
Drivers\SqlServer;Drivers\Firebird;Drivers\OracleODPNET;Drivers\Access;Drivers\DB2;
Drivers\OracleMSOracle;Drivers\SybaseAse;Drivers\SybaseAsa;
Drivers\MySql;Drivers\PostgreSql;TaskPerformers;ReferencedAssemblies;
Plugins;TypeConverters" />
<dependentAssembly>
<assemblyIdentity name="Oracle.DataAccess" publicKeyToken="89B483F429C47342" />
<bindingRedirect oldVersion="10.1.0.000-10.2.0.100" newVersion="10.2.0.100" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Oracle.DataAccess" publicKeyToken="89B483F429C47342" />
<bindingRedirect oldVersion="2.102.2.20-2.112.6.20" newVersion="10.2.0.100" />
</dependentAssembly>
</assemblyBinding>
</runtime>
<system.data>
<DbProviderFactories>
<add name="Oracle Data Provider for .NET" invariant="Oracle.DataAccess.Client" description="Oracle Data Provider for .NET" type="Oracle.DataAccess.Client.OracleClientFactory, Oracle.DataAccess, Version=10.2.0.100, Culture=neutral, PublicKeyToken=89b483f429c47342" />
<!-- Firebird -->
<add name="Firebird Client Data Provider"
invariant="FirebirdSql.Data.FirebirdClient"
description=".Net Framework Data Provider for Firebird"
type="FirebirdSql.Data.FirebirdClient.FirebirdClientFactory, FirebirdSql.Data.FirebirdClient, Version=2.1.0.0, Culture=neutral, PublicKeyToken=3750abcc3150b00c" />
<!-- PostgreSql -->
<add name="PostgreSql Client Data Provider"
invariant="Npgsql"
description=".Net Framework Data Provider for PostgreSql"
type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.4.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
</DbProviderFactories>
</system.data>
GAC contains entry:
Assembly name = Oracle.DataAccess
Version = 10.2.0.100
Public key token = 89b483f429c47342
It still returns the same message:
Exception message:
Exception type: ConfigurationErrorsException
Failed to find or load the registered .Net Framework Data Provider.