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Asked: 2026-05-23T20:01:37+00:00

I successfully use EF4 to build my database from scratch. My database is an

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I successfully use EF4 to build my database from scratch. My database is an SQL EXPRESS database file. I can manage this one with Sql Server Management Studio. So far so good.

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I noticed that if I open my database with the Server Explorer in Visual Studio, the next time I run the application I got errors.

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I also noticed that a new log file has been created. So now I have 2 log files.

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Below is my connectionstring:

<add name="DocumentManagerEntities" 
     connectionString="data source=.\SQLEXPRESS2008;Initial Catalog=DocumentManagerDB;AttachDBFilename=|DataDirectory|DocumentManagerDB.mdf;Integrated Security=SSPI;MultipleActiveResultSets=True" 
     providerName="System.Data.SqlClient" />

What’s wrong?

Thank you very much.

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1 Answer

  1. Editorial Team

    That maybe because multiple applications are trying to use your database at once. You need to close one connection to open another.

    This article notes that

    SQL Server Express Edition allows only a single connection to an .mdf
    file when you connect with a connection string that has User Instance
    set to true.

    Further more

    When you connect to a local database project, Visual Web Developer
    connects to the SQL Server Express Edition database with user
    instances enabled, by default. For example, the following code example
    shows a typical connection string used by Visual Web Developer to
    connect to a SQL Server Express Edition database.

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