More actions ▼
Up Query using LINQ

Paging queries

Last modified on October 15, 2012 19:38
Contents

A paged query is a query which returns a subset, or page, of query results at a time. At its simplest level, paging is performed using the LINQ Take and Skip operators.


For example, if we think of a page size as being 50 entities, then we can fetch any page n of Customers, using the following kind of query logic:

C#
var pageNumber = 1;
var pageSize = 50;
var pagedQuery = _em1.Customers.Skip((pageNumber-1)*pageSize).Take(pageSize);

var customersOnFirstPage = pagedQuery.ToList();

pageNumber++
var customersOnNextPage = pagedQuery.ToList();

pageNumber = 17;
var customersOnPage17 = pagedQuery.ToList();
VB
Dim pageNumber = 1
Dim pageSize = 50
Dim pagedQuery = _em1.Customers.Skip((pageNumber - 1) * pageSize).Take(pageSize)

Dim customersOnFirstPage = pagedQuery.ToList()

pageNumber = pageNumber + 1
Dim customersOnNextPage = pagedQuery.ToList()

pageNumber = 17
Dim customersOnPage17 = pagedQuery.ToList()


EntityQueryPager

The EntityQueryPager<T> is an integrated paging engine that can fetch pages from a combined view of the server-side datasource plus the client-side cache. It can operate either synchronously or asynchronously, and can be used in both WinClient and Silverlight applications.

To use the EntityQueryPager you provide it with a base EntityQuery, sort information, and page size. You then call its various "MoveTo" paging methods to move forwards and backwards within the overall result set. The EntityQueryPager handles the difficult problems which arise when paging through an editable collection, as it can determine the appropriate query strategy based on what has been cached, and also performs page marking.

See the code samples for a sample application.

Created by DevForce on February 17, 2011 14:38

Navigation

Tag Cloud

  1. Data Binding
  2. Data Sources
  3. Design Views
  4. Validation
  5. Anonymous
  6. Architecture
  7. ASP.NET
  8. Asynchronous
  9. Attach
  10. Azure
  11. CacheQueryOptions
  12. Caching
  13. Closure
  14. Cocktail
  15. code first
  16. Code Generation
  17. Code Sample
  18. Concurrency
  19. Configure
  20. Cookbook
  21. Coroutine
  22. Create
  23. Debug
  24. Delete
  25. Deploy
  26. DevForce 2012
  27. DevForce-Caliburn framework
  28. Disconnect
  29. Discovery
  30. Display
  31. Dynamic query
  32. EDM
  33. EDMX
  34. Entity cache
  35. Entity Framework
  36. EntityAspect
  37. EntityCache
  38. EntityKey
  39. EntityKeyQuery
  40. EntityManager
  41. EntityProperty
  42. EntityQuery
  43. EntityQueryOperation
  44. EntitySaveOperation
  45. EntityServer
  46. EntityServerSaveInterceptor
  47. EntityState
  48. EntityVersion
  49. ESQL
  50. Exception
  51. Extensibility
  52. Extension
  53. Faking
  54. Fetching
  55. FetchStrategy
  56. IIS
  57. Include
  58. Interception
  59. iOS
  60. IVerifierProvider
  61. JavaScript
  62. LINQ
  63. Localization
  64. Log
  65. MEF
  66. MergeStrategy
  67. Metadata
  68. MetadataType
  69. Model
  70. Multi-threading
  71. MVVM
  72. Navigation
  73. Object Mapping
  74. ObjectDataSource
  75. OData
  76. Offline
  77. Paging
  78. Performance
  79. Persistence
  80. POCO
  81. Predicate
  82. PredicateBuilder
  83. PredicateDescription
  84. Prism
  85. Property Interceptors
  86. PropertySortSelector
  87. Push
  88. Query
  89. Query cache
  90. Query Inversion
  91. QueryStrategy
  92. Refetch
  93. Refresh
  94. Release Notes
  95. Sample Application
  96. Save
  97. SaveOptions
  98. SaveResult
  99. SaveStatus
  100. Saving
  101. Security
  102. Serialization
  103. Silverlight
  104. Stored Procedure
  105. Telerik
  106. Template
  107. Test
  108. ToQuery
  109. Tour
  110. Transactions
  111. Troubleshooting
  112. Validation
  113. Verifier
  114. VerifierEngine
  115. Video
  116. Visual Studio
  117. WCF
  118. WinForms
  119. WIP
  120. WPF

Spaces

 | 2009Documentation | Documentation

This wiki is licensed under a Creative Commons 2.0 license. XWiki Enterprise 3.2 - Documentation. Copyright © 2015 IdeaBlade