devexpress-xaf-filtering-xpo

DevExpress XAF — Filtering (XPO Sub-Skill)

This sub-skill extends devexpress-xaf-filtering with XPO-specific filtering patterns. The base skill covers CriteriaOperator syntax, IObjectSpace methods, and XAF filtering infrastructure — this skill covers the XPO layer underneath.

When to Use This Skill

Use this skill (in addition to the base skill) when:

• The XAF project uses XPO as its ORM
• You need to filter XPCollection<T> with CriteriaOperator
• You need XPQuery<T> (LINQ to XPO) for type-safe queries
• You need XPView for lightweight read-only projections
• You need to build criteria programmatically using BinaryOperator, GroupOperator, FunctionOperator
• You need server-mode data sources with filtering
• You need Session.FindObject or Session.GetObjects

Prerequisites & Installation

XPO filtering uses the same core criteria classes as the base filtering skill, plus XPO-specific collection and session APIs.

NuGet Packages

Package	Purpose
DevExpress.Xpo	Session, UnitOfWork, XPCollection<T>, XPQuery<T>, XPView, XPInstantFeedbackSource, XPServerCollectionSource
DevExpress.ExpressApp.Xpo	XPObjectSpace — bridges IObjectSpace to XPO Session
DevExpress.Data	CriteriaOperator, BinaryOperator, GroupOperator, and all criteria classes (DevExpress.Data.Filtering namespace)

These packages are included in XPO-based XAF projects created from the template.

Using Statements

using DevExpress.Data.Filtering;      // CriteriaOperator, BinaryOperator, GroupOperator, etc.
using DevExpress.Xpo;                 // Session, XPCollection, XPQuery, XPView, SortProperty
using DevExpress.ExpressApp.Xpo;      // XPObjectSpace — access Session from IObjectSpace

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CriteriaOperator Class Hierarchy

All criteria operators live in DevExpress.Data.Filtering:

CriteriaOperator (abstract)
├── BinaryOperator          — a op b (==, !=, <, >, <=, >=)
├── GroupOperator            — AND / OR of multiple operands
├── UnaryOperator            — NOT, IsNull
├── FunctionOperator         — built-in & custom functions
├── ContainsOperator         — collection element check
├── InOperator               — value IN (list)
├── BetweenOperator          — value BETWEEN (low, high)
├── AggregateOperand         — aggregate over collection
├── JoinOperand              — join non-associated objects
├── OperandProperty          — property reference
├── OperandValue             — literal value
└── ConstantValue            — compile-time constant