EF 4 Code First:无法检查模型兼容性,因为EdmMetadata类型未包含在模型中

Question

我正在尝试使用EF 4 Code First模式.我的初始化代码如下:

创建模型构建器:

private static DbModelBuilder CreateModelBuild()
{
    var builder = new DbModelBuilder();

    //add entity classes about 12 of them

    builder.Conventions.Remove<IncludeMetadataConvention>();
    return builder;
}

创建会话:

private bool BuildSqlServerSession(DbModelBuilder builder)
{
    var model =
    builder.Build(new SqlConnection(@"connection string"));
    var cm = model.Compile();
    var context = new LittlePOSContext(cm);
    var dbExists = context.Database.Exists();
    _session = new EFSession(context);
    return dbExists;
}

这在我第一次运行代码时有效.但是当第二次运行并尝试使用context.Add(myEntity)我添加一个对象时,我得到以下异常:

Model compatibility cannot be checked because the EdmMetadata type was not 
included in the model. Ensure that IncludeMetadataConvention has been added 
to the DbModelBuilder conventions.

我试过删除以下行:

builder.Conventions.Remove<IncludeMetadataConvention>();

但我仍然得到错误.

Answer 1

嗯,这感觉有点傻,但真正的罪魁祸首是声明:

Database.SetInitializer(new DropCreateDatabaseIfModelChanges<MyContext>());

它似乎DropCreateDatabaseIfModelChanges与Code First方法不兼容,或者是其他一些我还不了解的神秘事物.