C # tips for querying Entity Framework NoTracking

When using Entity Framework for query, if you only need to display the object without saving it, you can use AsNoTracking () to obtain data.

This improves the query performance.

The Code is as follows:

var context = new Entities(connectStr);var contentlist = context.Set<Content>().AsQueryable().AsNoTracking();　　

However, if you want to modify and save the data after obtaining the data, it cannot be reflected in the database.

For example:

 context =  contentlist = context.Set<Content> content = contentlist.Where(o => o.Id == = 

After the modification, the database was Commit. After reading the data again, we found that the Id of the data is still 18.

 

In addition, if you delete the data obtained through AsNoTracking, an error is returned.

For example:

var context = new Entities(connectStr);var contentlist = context.Set<Content>().AsQueryable().AsNoTracking();var content = contentlist.Where(o => o.Id == 18).FirstOrDefault();context.Set<Content>().Remove(content);context.SaveChanges();

System. InvalidOperationException will be thrown after execution,

The reason is: When zookeeper has been added to the ObjectStateManager, the zookeeper has been removed.

The object cannot be deleted because it cannot be found in ObjectStateManager.