实体框架:存储实体而不保存到数据库

Question

如何在不保存到数据库的情况下在ObjectContext中存储临时项？

上下文存储在HttpContext中,按类提供:

public static class HttpContextExtension
{
    public static MyEntityDataModelContainer GetMyContext(this HttpContext httpContext)
    {
        if (httpContext.Items["MyEntityDataModelContainer"] == null)
        {
            httpContext.Items.Add("MyEntityDataModelContainer", new MyEntityDataModelContainer());
        }

        return (MyEntityDataModelContainer)httpContext.Items["MyEntityDataModelContainer"];
    }
}

有两个空页:1)FirstPage.aspx.cs:

public class FirstPage : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // crete new item
        MyEntity newTemporaryItem = new MyEntity { MyEntityID = Guid.NewGuid() };
        // attach them to Context
        HttpContext.Current.GetMyContext().MyEntitySet.Attach(newTemporaryItem);
        // save changes
        HttpContext.Current.GetMyContext().SaveChanges();

        // get all attached to Context items
        var addedItems = (from se in HttpContext.Current.GetMyContext().ObjectStateManager.GetObjectStateEntries(EntityState.Unchanged)
                          where se.Entity is MyEntity
                          select se.Entity).AsQueryable();
        int CountInFirstPage = addedItems.Count();
    }
}

所以,CountInFirstPage = 1.

2)SecondPage.aspx.cs:

public class FirstPage : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // get added in First page items From HttpContext
        var addedItems = (from se in HttpContext.Current.GetMyContext().ObjectStateManager.GetObjectStateEntries(EntityState.Unchanged)
                          where se.Entity is MyEntity
                          select se.Entity).AsQueryable();
        int CountInSecondPage = addedItems.Count();
    }
}

这里CountInSecondPage = 0.

哪里我错了？

Answer 1

我说得对吗，第二页是第二个请求？

在这种情况下，您将拥有一个新的 HttpContext.Items 集合，并且上次请求中的值将消失。在这种情况下，请考虑使用会话来存储这些值。

脚注： EntityContext 只能用于一个请求，因此可以存储在 HttpContext.Items 集合中，但绝不能作为 Session 值！此处仅存储结果（例如计数）。