即使我使用IQueryable，代码首先连接到数据库的实体框架

Question

我正在尝试使用现有数据库创建实体框架代码优先方案。 问题是，当我运行程序时，即使我使用IQueryable<> ，也会尝试连接到数据库。请阅读代码中的评论以获取更多详细信息：

static void Main(string[] args)
{
    using (SomeContext db = new SomeContext())
    {
        // This one does not connects to database. 
        // If I disable my network connection this code will still be executed
        IQueryable<Activity> allActivitiesQuery = db.ActivitySet;

        // This one does connects to database. 
        // If I disable my network connection this query will throw exception
        IQueryable<Activity> filteredActivitiesQuery = db.ActivitySet
            .Where(activity => !string.IsNullOrEmpty(activity.FirstProperty));
    }

    //If I use same context again it will not connect to database
    using (SomeContext db = new SomeContext())
    {
        //Both statements will be executed even network connection is closed
        IQueryable<Activity> allActivitiesQuery = db.ActivitySet;
        IQueryable<Activity> filteredActivitiesQuery = db.ActivitySet
            .Where(activity => !string.IsNullOrEmpty(activity.FirstProperty));
    }
}

如何防止此行为？当我首先使用数据库并从数据库生成模型时，这种情况并未发生。 当我仅使用IQueryable<>时，如何阻止对数据库的连接请求？

---

其他详细信息：

如果您需要 ，以下是我的模特：

//model
public class Activity
{
    public string FirstProperty { get; set; }
    public string SecondProperty { get; set; }
    public string ThirdProperty { get; set; }
}

//mapping details
public class ActivityMap : EntityTypeConfiguration<Activity>
{
    public ActivityMap()
    {
        //Primary key
        ..........

        //Properties
        .............

        //Table & column mappings 
        .......................
    }
}

//Context details
public class SomeContext : DbContext
{
    static SomeContext()
    {
        Database.SetInitializer<SomeContext>(null);
    }

    public SomeContext()
        : base("Name=SomeContext")
    {
        this.Configuration.LazyLoadingEnabled = false;
        this.Configuration.AutoDetectChangesEnabled = false;
    }

    public DbSet<Activity> ActivitySet { get; set; }

    // Add mapping configuration for code first POCO objects
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add(new ActivityMap());
    }
}