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The ADO.NET E n tity Framework: Tips & Tricks. Shyam Pather (spather@microsoft.com) Development Manager Microsoft Session Code: DTL312. Julie Lerman made these slides. Mentor/Consultant jlerman@thedatafarm.com thedatafarm.com/blog LearnEntityFramework.com. 10 Tips & Tricks .
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The ADO.NET Entity Framework: Tips & Tricks Shyam Pather (spather@microsoft.com) Development Manager Microsoft Session Code: DTL312
Julie Lerman made these slides Mentor/Consultant jlerman@thedatafarm.com thedatafarm.com/blog LearnEntityFramework.com
10 Tips & Tricks • Solving Pain Points • Foreign Keys: Reading • : Writing • : Set Default Value • Improve Inefficient Store Queries • Use Random Results from Stored Procedures • Use ObjectQuery methods with L2E • Using EF More Effectively • Create Generic Queries • Find Exception Handling Details • Encapsulate Query Execution • Improve Query Performance
2. Set Reference without Ref Object from Single EntityKey Property Order.CustomerReference.EntityKey = new EntityKey("MyEntities.Customers", "PersonID", 1) from Multiple EntityKey Properties vareKeyValues = new KeyValuePair<string, object>[] { new KeyValuePair<string, object>(“PropertyA", 12), new KeyValuePair<string, object>(“PropertyB", 103) }; EntityKey ekey= new EntityKey(“MyEntities", eKeyValues); instance.EntityRef.EntityKey=ekey;
3. Set Default Entity Reference Value Create Constructor in Entity's Partial Class C# Public Customer() { CustomerTypeReference.EntityKey = new EntityKey("MyEntities.CustomerTypes", “TypeID", 1) } • VB • Public Sub New() • CustomerTypeReference.EntityKey = • New EntityKey("MyEntities.CustomerTypes", “TypeID", 1) • End Sub
Undesirable Store Queries LINQ to Entities Query From p In context.PeopleWhere p.LastName.StartsWith(“K") • Resulting T-SQL Query • SELECT [Extent1].[PersonID] AS [PersonID], ... • WHERE (CAST(CHARINDEX(N'T', Extent1].[LastName]) • AS int)) = 1 !
4. Control Store Query w/ ESQL Entity SQL SELECT VALUE p FROM EFEntities.People AS p WHERE p.LastName LIKE “T%” Query Builder Methodscontext.People.Where("it.LastName LIKE 'T%'") • Resulting T-SQL • SELECT [Extent1].[PersonID] AS [PersonID], • WHERE [Extent1].[LastName] LIKE 'T%'
Bonus Tip! Testing ESQL Expressions eSql Blast! code.msdn.com/adonetefx
Stored Procs Return Non-Entity • Requires lots of manual editing of the model, MSL and SSDL to create an entity that matches the return value CREATE PROCEDURE OrdersBySalesPersonbyDate AS SELECT MIN(Person.FirstName) as First, MIN(Person.LastName) as Last, COUNT(Orderid) as OrderCount FROM … !
5. Use Views in Place of Sprocs CREATE VIEW OrdersBySalesPersonbyDate AS SELECT MIN(Person.FirstName) as First, MIN(Person.LastName) as Last, COUNT(Orderid) as OrderCount FROM … • Wizard creates all entity metadata elements • Other benefits • View is composable • Use in queries • Change Tracking (use Stored Procs for DML)
ObjectQuery Special Methods in L2E Include from p in context.Orders.Include(“Customer”) select p OfType from p in context.People.OfType<Customer> select p MergeOption context.People.MergeOption=MergeOption.NoTracking; from p in context.People select p; Execute ??? ToTraceString ??? !
6. Cast L2E to Get ObjectQuery Methods • C# • var l2eQuery=from c in context.Customers select c ; • varstoreSQL=((ObjectQuery)l2eQuery).ToTraceString(); • VB • Dim l2eQuery=From c In context.Customers Select c • Dim storeSQL = CType(l2eQuery, ObjectQuery).ToTraceString
Redundant L2E Queries Country Reference List List<Country> GetCountries() { return context.Countries.OrderBy(c => c.Name) .ToList(); } Account Type Reference List List<AccountType> GetAccountTypes() { return context.AccountTypes.OrderBy(a => a.TypeName) .ToList(); } Product Reference List List<Product> GetProducts() { return context.Products.OrderBy(p => p. Name) .ToList(); } !
7. Build Reusable, Generic Queries public static List<TEntity> GetReferenceList<TEntity> (this ObjectContext context) context.GetReferenceList<Country> context.GetReferenceList(Of AccountType) context.GetReferenceList<Product>
UpdateExceptions Anonymity s Order B ? Person A Person B Order A db Error ? Person D Order C ? Order D Person C !
8. ObjectStateEntry & Entity Instance Are Provided in UpdateExceptions
Redundant Code around Queries var query=from p in context.People select p; try { var people=query.ToList(); } catch (EntityException) { ... } Catch (CommandExecutionException) { ... } var query2=from o in context.Orders select o; try { var orders =query2.ToList(); } catch (EntityException) { ... } Catch (CommandExecutionException) { ... } !
9. Encapsulate Query Execution Reusable Repository Methods public List<TEntity> ExecuteList<TEntity> (ObjectQuery<TEntity> objectQuery) public List<TEntity> ExecuteList<TEntity> (IQueryable<TEntity> L2EQuery) Calling Reusable Methods IEnumerable<Person> L2EQuery = from p in context.People select p; List<Person> people = dal.ExecuteList<Person>(L2EQuery); ObjectQuery oQuery = context.Orders; List<Order> orderList = dal.ExecuteList<Order>(oQuery);
Bonus Tip! Pre-Compile L2E Queries PreCompiled Query LINQ to Entities Query Store Query
Web Sites Lose Pre-Compiled L2E Queries • Short-lived ObjectContext used to compile • Pre-Compilation is repeated each time • App process loses benefit of pre-compilation • Big performance loss !
10. Cache Pre-Compiled Query Func Class Level Static Function static Func<MyEntities, IQueryable<Customer>> customerPCQ; Class Constructor public CustomerProvider() { if (customerPCQ == null) { customerPCQ = CompiledQuery.Compile<MyEntities, IQueryable<Customer>> (ctx => from cust in ctx.Customers where cust.Orders.Any() select cust ); } }
EF4 Removes Some of the Pain • Solving Pain Points • Foreign Keys: Reading • : Writing • : Set Default Value • Improve Inefficient Store Queries • Use Random Results from Stored Procedures • Use ObjectQuery methods with L2E • Using EF More Effectively • Create Generic Queries • Find Exception Handling Details • Encapsulate Query Execution • Improve Query Performance
Julie Lerman's Contact Info Again Julie Lerman jlerman@thedatafarm.com thedatafarm.com/blog LearnEntityFramework.com
My Contact Info spather@microsoft.com
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