我有这个问题时，我使用多个项目，启动项目与web。EntityFramework项目的config和app.config。

为了避免这个问题，你必须:

您需要连接字符串在开始*。配置文件。 您需要将EntityFramework DLL安装到引用中

你可以把连接字符串传递给EntityFramework，然后继续你的生活:

public partial class UtilityContext : DbContext
{
    static UtilityContext()
    {
        Database.SetInitializer<UtilityContext>(null);
    }

    public UtilityContext()
        : base("Data Source=SERVER;Initial Catalog=DATABASE;Persist Security Info=True;User ID=USERNAME;Password=PASSWORD;MultipleActiveResultSets=True")
    {
    }

    // DbSet, OnModelCreating, etc...
}

Add an App.Config file Set the project as startup project. Make sure you add the connection strings after entityFramework section: <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"/> </configSections> <connectionStrings> <!-- your connection string goes here, after configSection --> </connectionString>

确保你已经在启动项目的ROOT web.config中放置了连接字符串。

I know I'm kinda stating the obvious here, but it happened to me too - though I already HAD the connection string in my MVC project's Web.Config (the .edmx file was placed at a different, class library project) and I couldn't figure out why I keep getting an exception... Long story short, I copied the connection string to the Views\Web.Config by mistake, in a strange combination of tiredness and not-scrolling-to-the-bottom-of-the-solution-explorer scenario. Yeah, these things happen to veteran developers as well :)

添加ConnectionString到MVC项目Web。配置文件

如果你在解决方案中有多个项目，那么在你有真理App.config的地方开始安装项目。