要素的标注

要素的标注标注有两种方法，一个是添加TextElement到文档对象，另一种是基于要素的某个属性进行标注，它需要载入数据支持。第一种方法在P8中可以看到。下面介绍后一种方法：
Public sub Anno(byval pGeoFeatLyr as iGeofeaturelayer,byval field as string)
    Dim pGeoFeatLayer As IGeoFeatureLayer
pGeoFeatLayer = pGeoFeatLyr
         Dim pAnnoProps As IannotateLayerPropertiesCollection              
         pAnnoProps = pGeoFeatLyr.AnnotationProperties
         pAnnoProps.Clear()               必须执行这个语句，否则里面会默认有一个pAnnoLayerProps
         Dim pAnnoLayerProps As IAnnotateLayerProperties
         Dim pPosition As ILineLabelPosition
         Dim pPlacement As ILineLabelPlacementPriorities
         Dim pBasic As IBasicOverposterLayerProperties
         Dim pLabelEngine As ILabelEngineLayerProperties
         Dim pTextSyl As ItextSymbol         标注的文字格式，注意
         pTextSyl = New TextSymbol
         Dim pFont As stdole.StdFont
         pFont = New stdole.StdFont
         pFont.Name = "verdana"
         pFont.Size = 5
         pTextSyl.Font = pFont
         pTextSyl.Color = HSVColor(250, 160, 200)
         pPosition = New LineLabelPosition
         pPosition.Parallel = False
         pPosition.Perpendicular = True
         pPlacement = New LineLabelPlacementPriorities
         pBasic = New BasicOverposterLayerProperties
         pBasic.FeatureType = esriBasicOverposterFeatureType.esriOverposterPolyline
         pBasic.LineLabelPlacementPriorities = pPlacement
         pBasic.LineLabelPosition = pPosition
         pLabelEngine = New LabelEngineLayerProperties
         pLabelEngine.Symbol = pTextSyl
         pLabelEngine.BasicOverposterLayerProperties = pBasic
         pLabelEngine.Expression = field          field必须是这个样子——"[STATE_NAME]"
         pAnnoLayerProps = pLabelEngine
         pAnnoProps.Add(pAnnoLayerProps)
         pGeoFeatLyr.DisplayAnnotation = True
     AxMapControl.CtlRefresh(esriViewDrawPhase.esriViewBackground)
End sub
消除标注的方法也很简单，由于pGeoFeatLyr是一个全局变量，我们只要设置如下代码即可：
         pGeoFeatLyr.DisplayAnnotation = False
      AxMapControl.CtlRefresh(esriViewDrawPhase.esriViewBackground)