在实体框架C＃中将表实体分配给具有相同架构的另一个表实体

Question

I have two tables in my database with identical column names and column quantity. Table1 is a working table, where it is constantly being hit and iterated through. Table2 is an exact replica of Table1 and is only used to archive Table1. Every week, a few rows in Table1 get copied into Table2 and removed from Table1.

Now that you have some context...

Table1 and Table2 are converted into Entities in EntityFramework. I want to be able to either merge the two tables together in any fashion OR be able to assign each "item" to an identical "archiveItem" like the following:

var archiveObjects= new List<archiveObject>();
foreach(var object in objects)
{
    var objectConvertedToArchiveObject = (archiveObject) object;
    archiveObjects.Add(objectConvertedToArchiveObject);
}

There are 55 columns in each of these tables (entities). That is why I don't just assign each column (property).

Thanks for your help in advance!

Answer 1

There's no way in Entity Framework to "merge" two tables. Each entity is intrinsically tied to one table. If you need to get all the data, from both tables you can either:

1. Create a view at the database level and tie your entity to this view. In the view, you will merge the data from the two distinct tables. For your entity, you just need to decorate the class with [Table("YourViewName")] . However, views amongst other things are not indexed. It's fine if you intend to just pull all the data, but if you want to query into that data, the view is going to be a poor way to achieve that.

2. Have your two entities representing Table1 and Table2 both either inherit from a base class or implement an interface. You can then create a list of that base class or interface, query the data from each table individually, and then combine them into the same list:

    var combinedData = new List<ITable>(); combinedData.AddRange(db.Table1.ToList()); combinedData.AddRange(db.Table2.ToList());