Entity Framework Extended Library A library
the extends
the functionality of Entity Framework. Features Batch Update and Delete
Future Queries Audit Log Project Package and Source NuGet Package PM> Install-Package EntityFramework.Extended NuGet: http://nuget.org/List/Packages/EntityFramework.Extended Source: http://github.com/loresoft/EntityFramework.Extended Batch Update and Delete A current limitations of
the Entity Framework is that in order
to update or delete an entity you have
to first retrieve it into memory. Now in most scenarios this is just fine. There are however some senerios where performance would suffer. Also, for single deletes,
the object must be retrieved before it can be deleted requiring two calls
to the database. Batch update and delete eliminates
the need
to retrieve and load an entity before modifying it. Deleting //delete all users where FirstName matches
context.Users.Delete(u => u.FirstName == "firstname");
Update
//update all tasks with status of 1
to status of 2
context.Tasks.Update(
t => t.StatusId == 1,
t => new Task {StatusId = 2});
//example of using an IQueryable as
the filter for
the update
var users = context.Users
.Where(u => u.FirstName == "firstname");
context.Users.Update(
users,
u => new User {FirstName = "newfirstname"});
Future Queries
Build up a list of queries for
the data that you need and
the first time any of
the results are accessed, all
the data will retrieved in one round trip
to the database server. Reducing
the number of trips
to the database is a great. Using this feature is as simple as appending .Future()
to the end of your queries.
To use
the Future Queries, make sure
to import
the EntityFramework.Extensions namespace.
Future queries are created with
the following extension methods...
Future()
FutureFirstOrDefault()
FutureCount()
Sample
// build up queries
var q1 = db.Users
.Where(t => t.EmailAddress == "
[email protected]")
.Future();
var q2 = db.Tasks
.Where(t => t.Summary == "Test")
.Future();
// this triggers
the loading of all
the future queries
var users = q1.ToList();
In
the example above, there are 2 queries built up, as soon as one of
the queries is enumerated, it triggers
the batch load of both queries.
// base query
var q = db.Tasks.Where(t => t.Priority == 2);
// get total count
var q1 = q.FutureCount();
// get page
var q2 = q.Skip(pageIndex).Take(pageSize).Future();
// triggers execute as a batch
int total = q1.Value;
var tasks = q2.ToList();
In this example, we have a common senerio where you want
to page a list of tasks. In order for
the GUI
to setup
the paging control, you need a total count. With
Future, we can batch together
the queries
to get all
the data in one database call.
Future queries work by creating
the appropriate IFutureQuery object that keeps
the IQuerable.
The IFutureQuery object is then stored in IFutureContext.FutureQueries list. Then, when one of
the IFutureQuery objects is enumerated, it calls
back to IFutureContext.ExecuteFutureQueries() via
the LoadAction delegate. ExecuteFutureQueries builds a batch query from all
the stored IFutureQuery objects. Finally, all
the IFutureQuery objects are updated with
the results from
the query.
Audit Log
The Audit Log feature will capture
the changes
to entities anytime they are submitted
to the database.
The Audit Log captures only
the entities that are changed and only
the properties on those entities that were changed.
The before and after values are recorded. AuditLogger.LastAudit is where this information is held and there is a ToXml() method that makes it easy
to turn
the AuditLog into xml for easy storage.
The AuditLog can be customized via attributes on
the entities or via a Fluent Configuration API.
Fluent Configuration
// config audit when your application is starting up...
var auditConfiguration = AuditConfiguration.Default;
auditConfiguration.IncludeRelationships = true;
auditConfiguration.LoadRelationships = true;
auditConfiguration.DefaultAuditable = true;
// customize
the audit for Task entity
auditConfiguration.IsAuditable<Task>()
.NotAudited(t => t.TaskExtended)
.FormatWith(t => t.Status, v => FormatStatus(v));
// set
the display member when status is a foreign key
auditConfiguration.IsAuditable<Status>()
.DisplayMember(t => t.Name);
Create an Audit Log
var db = new TrackerContext();
var audit = db.BeginAudit();
// make some updates ...
db.SaveChanges();
var log = audit.LastLog;
