ArcGIS Engine获取单条要素的标注（LABEL）内容

众所周知，arcgis的标注设置是对整个图层的，那有没有办法获取某条要素的标注内容呢？当然有！！！

分两步，第一步先获取layer级别的IAnnotationExpressionParser对象，获取标注内容靠他了

            IAnnotationExpressionParser tAnnoExpParse = null;

            IAnnotateLayerPropertiesCollection tAnnotateLayerPropertiesCollection = tGeoFeatureLayer.AnnotationProperties;
            IAnnotateLayerProperties tAnnotateLayerProperties = null;
            IElementCollection tElementCollection = null;     
            if (tAnnotateLayerPropertiesCollection.Count > 0)
            {
                tAnnotateLayerPropertiesCollection.QueryItem(0, out tAnnotateLayerProperties, out tElementCollection, out tElementCollection);
                ILabelEngineLayerProperties tLabelEngineLayerProperties = tAnnotateLayerProperties as ILabelEngineLayerProperties;     
                //获取标注解析类
                IAnnotationExpressionEngine tAnnoExpEngine = tLabelEngineLayerProperties.ExpressionParser;
                if (tLabelEngineLayerProperties.IsExpressionSimple == true)
                {
                    tAnnoExpParse = tAnnoExpEngine.SetExpression("", tLabelEngineLayerProperties.Expression);
                }
                else
                {
                    tAnnoExpParse = tAnnoExpEngine.SetCode(tLabelEngineLayerProperties.Expression, "");
                }

第二步相对简单，关键函数是FindLabel

string labelValue = tAnnoExpParse.FindLabel(tFeature);

关于这种方法还有点疑问

首先，获取用SetExpression和SetCode这两个函数去获取IAnnotationExpressionParser感觉很怪，非得要赋值才能取值很有问题。

其次SetExpression和SetCode这两个函数有些参数不理解，所以只是给了空值，这也是个隐患