The 'DbProviderFactories' section can only appear once per config file

Question

We are receiving this error when calling a WCF .net 4.0 service using entity framework.

The 'DbProviderFactories' section can only appear once per config file

It is the first app on the server using EF and other .net 4.0 WCF services are not receiving this error.

Is there any way to correct this error with out editing the machine config file on the server?

Answer 1

The installation for IBM DB2 .NET provider, causes an empty DbProviderFactories, see below. Just delete the second empty entry DbProviderFactories

<system.data>
    <DbProviderFactories>
        <add name="IBM DB2 for i .NET Provider" invariant="IBM.Data.DB2.iSeries" description=".NET Framework Data Provider for IBM i" type="IBM.Data.DB2.iSeries.iDB2Factory, IBM.Data.DB2.iSeries, Version=12.0.0.0, Culture=neutral, PublicKeyToken=9cdb2ebfb1f93a26" />
    </DbProviderFactories>
    <DbProviderFactories />
</system.data>

Answer 2

Maybe you could create web.config entries which override any machine-wide settings you want changed.

Described here:

Override machine.config by web.config

Putting the <clear /> instruction inside of the DbProviderFactories tags in the web config to clear out and then override the duplicate entries made in the machine config. Thus doing a hack-work around of the error in the machine.config.

Answer 3

You have to update Machine.config file located in the below paths.

• C:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG\Machine.Config
• C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\Machine.Config

For 64-bit machines, Machine.config will be located in ...\Framework64\...

The block to pay attention to is this:

<system.data>
    <DbProviderFactories>
        <add name="IBM DB2 for i5/OS .NET Provider" invariant="IBM.Data.DB2.iSeries" description=".NET Framework Data Provider for i5/OS" type="IBM.Data.DB2.iSeries.iDB2Factory, IBM.Data.DB2.iSeries, Version=12.0.0.0, Culture=neutral, PublicKeyToken=9cdb2ebfb1f93a26"/>
        <add name="Microsoft SQL Server Compact Data Provider" invariant="System.Data.SqlServerCe.3.5" description=".NET Framework Data Provider for Microsoft SQL Server Compact" type="System.Data.SqlServerCe.SqlCeProviderFactory, System.Data.SqlServerCe, Version=3.5.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"/>
        </DbProviderFactories>
<!-- This is the line to remove - empty element --><DbProviderFactories/>
</system.data>