join and relate

添加、删除连接（Join）和关联（Relate）VBA实例

内容摘要
ArcMap里面可以通过属性字段为两个图层建立或删除连接和关联，怎样使用VBA或Engine完成同样的工作呢？
这里主要用到IDisplayRelationshipClass.DisplayRelationshipClass方法，如下为实现的VBA代码：
过程描述
Private Sub AddJoin_Relation_Click()
    Dim pFeatLayer As IFeatureLayer
    Dim pDispTable As IDisplayTable
    Dim pFCLayer As IFeatureClass
    Dim pTLayer As ITable
   
    Dim pTabCollection As IStandaloneTableCollection
    Dim pStTable As IStandaloneTable
    Dim pDispTable2 As IDisplayTable
    Dim pTTable As ITable
    Dim pMemRelFact As IMemoryRelationshipClassFactory
    Dim pRelClass As IRelationshipClass
    Dim pDispRC As IDisplayRelationshipClass
   
    Set pFeatLayer = GetLayer(0) ' MapControl1.Layer(0)
   
    Dim pDoc As IMxDocument
    Set pDoc = ThisDocument
    Dim pMap As IMap
    Set pMap = pDoc.ActiveView
    Set pTabCollection = pMap
    If pTabCollection.StandaloneTableCount = 0 Then
        Exit Sub
    End If
   
    Set pDispTable = pFeatLayer
    Set pFCLayer = pDispTable.DisplayTable
    Set pTLayer = pFCLayer
    Set pDispRC = pFeatLayer
   
    Set pStTable = pTabCollection.StandaloneTable(0)
   
    Set pDispTable2 = pStTable
    Set pTTable = pDispTable2.DisplayTable
    Set pMemRelFact = New MemoryRelationshipClassFactory
    Set pRelClass = pMemRelFact.Open(pStTable.Name, pTTable, "id", pTLayer, "省行政中心", "forward", "backward", esriRelCardinality.esriRelCardinalityOneToMany)    '这里参数根据具体数据和需求设置，详细信息可参照开发帮助文档

    '增加连接Join
    pDispRC.DisplayRelationshipClass pRelClass, esriJoinType.esriLeftOuterJoin
     
    '增加关系 --Relate
    Dim pRelClassCollEdit As IRelationshipClassCollectionEdit
    Set pRelClassCollEdit = pFeatLayer
    pRelClassCollEdit.AddRelationshipClass pRelClass
    Set pDispRC = pFeatLayer
    If Not pDispRC.RelationshipClass Is Nothing Then
        MsgBox "建立关联时：" & pDispRC.RelationshipClass.OriginClass.AliasName
    End If
End Sub

'删除连接和关联
Private Sub RemoveJoinRelation_Click()
    Dim pFeatLayer As IFeatureLayer
    Dim pDispRC As IDisplayRelationshipClass
    Dim pRelationshipClassCollectionEdit As IRelationshipClassCollectionEdit
   
    Set pFeatLayer = GetLayer(0) ' MapControl1.Layer(0)
    Set pRelationshipClassCollectionEdit = pFeatLayer
   
    Set pDispRC = pFeatLayer
   
    If Not pDispRC.RelationshipClass Is Nothing Then
        MsgBox "删除关联前：" & pDispRC.RelationshipClass.OriginClass.AliasName
    End If
   
    '删除Relate
    Call pRelationshipClassCollectionEdit.RemoveAllRelationshipClasses
   
    '删除所有Join
    pDispRC.DisplayRelationshipClass Nothing, esriJoinType.esriLeftOuterJoin    '这里第一个参数传入Nothing即可完成删除
   
    Set pDispRC = pFeatLayer
    If Not pDispRC.RelationshipClass Is Nothing Then
        MsgBox "删除关联后：" & pDispRC.RelationshipClass.OriginClass.AliasName
    End If

End Sub

关联后的表，查询时可以使用 IDisplayFeatureClass来查询

Dim pFeatureCursor As IFeatureCursor
Dim pFeature As IFeature
Dim pFClass As IFeatureClass
pFClass = pGeoFeatureLayer.DisplayFeatureClass
pFeatureCursor = pFClass.Search(Nothing, False)