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Editorial Team
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Asked: 2026-05-27T01:58:31+00:00

I have a library that I have created that depends on EF Codefirst for

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I have a library that I have created that depends on EF Codefirst for DB interaction. I am also using EntityMigrations Alpha 3. When I use the library in my main application (WPF) everything works fine and as expected. Another part of the system uses Excel and retrieves information using the same library via an additional COM class in between.

In the Excel scenario, as soon as it tries to connect to the database, it throws up an exception to do with “The Provider did not return a ProviderManifestToken”.

I’m really not sure why I’m only getting the error when I go through Excel/COM. In both scenarios I can confirm that the same DB connection string is being used. THe method to retrieve the DB Connection string is also the same – they use a shared config file & loader class.

Any suggestions welcome.

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1 Answer

  1. Editorial Team

    Issue resolved.

    I had also created a custom DBIntializer and part of the intialization calls upon EntityMigrations to ensure the DB is up to date. The custom migration calls the default constructor on your context. By convention this will either dynamically use it’s own connection string for SQLExpress(I don’t have installed) or try to look for an entry in your config file (I don’t have this either for the dll – config comes from hosting apps).

    This is what is causing the failure when being used from Excel(In my scenario). The Migration will be newing up an instance of the context using the default constructor. This means that a config entry for the connection string is required or it uses the default process(SQLExpress). When being used from Excel in a COM env – no config file exists.

    Moving the migration out of the Initialization strategy means I no longer have a problem.

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