Tech·Ed North America 2009 6/5/2018 6:10 PM © 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

The ADO.NET Entity Framework: Tips & Tricks Tech·Ed  North America 2009 6/5/2018 6:10 PM The ADO.NET Entity Framework: Tips & Tricks Julie Lerman The Data Farm jlerman@thedatafarm.com DTL312 © 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

Julie Lerman 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

EF Model Hides Foreign Key ! EF Model Hides Foreign Key

1. Get FK Value When No Reference Object Is Available

2. Set Reference without Ref Object from Single EntityKey Property Order.CustomerReference.EntityKey = new EntityKey("MyEntities.Customers", "PersonID", 1) from Multiple EntityKey Properties var eKeyValues = 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 ! Undesirable Store Queries LINQ to Entities Query From p In context.People Where 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 Methods context.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 ! Stored Procs Return Non-Entity CREATE PROCEDURE OrdersBySalesPersonbyDate AS SELECT MIN(Person.FirstName) as First, MIN(Person.LastName) as Last, COUNT(Orderid) as OrderCount FROM … Requires lots of manual editing of the model, MSL and SSDL to create an entity that matches the return value

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 ! ObjectQuery Special Methods in L2E Include from p in context.Orders.Include(“Customer”) select p OfType from p in context.People.OfType<Customer> MergeOption context.People.MergeOption=MergeOption.NoTracking; from p in context.People select p; Execute ??? ToTraceString

6. Cast L2E to Get ObjectQuery Methods var l2eQuery=from c in context.Customers select c ; var storeSQL=((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) Product Reference List List<Product> GetProducts() { return context.Products.OrderBy(p => p. Name)

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 ! 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 ! 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) (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 LINQ to Entities Query PreCompiled Query Store Query

Web Sites Lose Pre-Compiled L2E Queries ! 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

Contact Julie Lerman jlerman@thedatafarm.com thedatafarm.com/blog LearnEntityFramework.com

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Required Slide 6/5/2018 6:10 PM © 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION. © 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.