Post on 03-Apr-2020
Agenda
The data access layer and your options
Patterns for keeping entities consistent
Patterns for managing entity differences
Data access technology assessment
Other data access challenges
Summary and questions
Layers & Relationships
ConsiderationsDomain complexity
Developer experience
Greenfield vs. brownfield
Desired approach: data, code, or model first?
Object/schema fidelity
Two OptionsKeep entities consistent
Manage their differences
Data Access Layer DataStorage
BusinessLogic Layer
BusinessLogicLayer
Data Storage
Keeping Entities Consistent
Recommended when domain is less complex
Restricts object-oriented design options
Can benefit from code generation strategies
More difficult to evolve over time, but easier to manage
Common patternsRow Data Gateway
Table Data Gateway
Table Module
Active Record
Record Set
We have choicesShape of the objects
How to combinedata and logic
Pre-Built Types
Record Set (DataSet)Contains the data as rows and columns
Table Data GatewayEncapsulates all SQL
Can return record sets
Table ModuleAccepts a record set
Contains business logic
when objects and schema have a simple relationship
RowsColumns
RecordSet
Find() : RecordSetUpdate(a, b, c)Insert(a, b, c)Delete(id)
TableDataGateway
Process(RecordSet)Calculate(RecordSet)
TableModule
Custom Types
Row Data GatewayRepresents a table’s rowIncludes all CRUD capability
Transaction ScriptContains business logic
Active RecordRepresents a table’s rowContains business logicIncludes all CRUD capability
ID : longFirstName : stringLastName : stringUpdate(first, last)Insert(first, last)Delete(id)
RowDataGateway
ID : longFirstName : stringLastName : stringUpdate(first, last)Insert(first, last)Delete(id)Process()
ActiveRecord
ProcessCostChange()CalculateAdjustment()
TransactionScript
when objects and schema have a simple relationship
Managing Entity Differences
Appropriate for complex domain logic
Requires more developer experience
Can leverage more OO (GoF) design patterns
Appropriate for apps that evolve over time
Common patternsDomain Model
Data Mapper
Repository
Unit of Work
Specification
Storefront Overview
SQLServer
ASP.NETMVC
DataServices
Customer Retailer
Broker
• Manages product information
• Maintains inventory
• Processes and ships orders
IE WPF
Silverlight
• Collects a percentage from each sale• Views sales & site usage reports
• Searches for products
• Buys products• Views order
status• Rates products
and retailers
Domain Model & Mapping
Domain ModelAn object model that represents the domain
Contains the combination of data and business logic
Two basic optionsMay be robust and leverage OO principles
May be straightforward in less complex scenarios
May have no knowledge of data access technology
Data MapperRepresents an association of types and properties across the domain model and data model
Almost always aware of the data access technology
Implementations are often included in O/RM solutions
Mapping support varies
Repository
Collection-type interface to data access
Mediates between domain model and mapper
Implementations are specific to a technology
GetById(id)GetAll()Add(object)Update(object)Delete(id)
Repository
Unit of Work
Maintains a list of new, changed and deleted objects and coordinates persisting changes
Can be used across multiple repositories
SubmitChanges()CancelChanges()
UnitOfWork
Specification/Query Object
An object that represents the criteria of a query
Allows queries to be easier to manage
Avoids the need for a method for each query
Field : stringValue : objectOperator : OpEnum
Specification
Technology Assessment
ADO.NETDataSet
DataAdapter
DataReader
LINQ to SQLO/RM for simple mappings
ADO.NET Entity FrameworkO/RM for more complex mappings
Related Challenges
Domain Model ResponsibilitiesSerialization (DTOs)
Data binding
Edit tracking
Validation
Domain Model RepresentationsSubset of the type
View models
Summary
Steps for making choices1. Determine consistency possibilities between the
domain model and the data modelKeep entities consistent
Manage their differences
2. Choose shape of the typesPre-built
Custom built
3. Determine how to attach the business logicInfluenced by the shape of the types
Resources
Don’s email: dons@microsoft.com
Project’s community site: http://dataguidance.codeplex.com
Patterns of Enterprise Application Architecturehttp://www.martinfowler.com/eaaCatalog
The Microsoft Patterns & Practices Teamhttp://microsoft.com/practices
© 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,
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