添加Labels的两种方法

private void AddLabel(IFeatureLayer pLayer,string fieldname,ITextSymbol Symbol)
        {

            container.DeleteAllElements();

            IFeatureClass pClass = pLayer.FeatureClass;
            IFields pFields = pClass.Fields;
            int index =  pFields.FindField(fieldname);

            ITextElement pTextElement;
            IEnvelope pEnv = null;
            IElement pElement = null;
            //pTextElement.ScaleText = true;
            //pTextElement.Symbol = Symbol;

            IFeatureCursor pCursor = pClass.Search(null, false);
            IFeature pFeature;
            IPoint point;
            pFeature = pCursor.NextFeature();
            while (pFeature != null)
            {
                pEnv = pFeature.Extent;
                point = new PointClass();
                point.PutCoords((pEnv.XMin + pEnv.XMax) * 0.5, (pEnv.YMax + pEnv.YMin) * 0.5);

                pTextElement = new TextElementClass();
                pTextElement.Symbol = Symbol;
                pTextElement.ScaleText = true;
                pTextElement.Text = pFeature.get_Value(index).ToString();

                pElement = pTextElement as IElement;
                pElement.Geometry = point;

                container.AddElement(pElement, 0);
                pFeature = pCursor.NextFeature();
            }
            axMapControl1.Refresh();
        }

以上为第一种方法，另一种方法（利用提供的接口）：

 private void Label(IFeatureLayer pLayer, string fieldname, ITextSymbol Symbol)
        {
            IGeoFeatureLayer pGeoFeaturelayer = pLayer as IGeoFeatureLayer;
            IAnnotateLayerPropertiesCollection annotLayercol = pGeoFeaturelayer.AnnotationProperties;
            annotLayercol.Clear();

            IBasicOverposterLayerProperties basicoverPost = new BasicOverposterLayerPropertiesClass();
            basicoverPost.BufferRatio = 0.2;
            switch (pLayer.FeatureClass.ShapeType)
            {
                case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolygon:
                    basicoverPost.FeatureType = esriBasicOverposterFeatureType.esriOverposterPolygon;
                    break;
                case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolyline:
                    basicoverPost.FeatureType = esriBasicOverposterFeatureType.esriOverposterPolyline;
                    break;
                case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPoint:
                    basicoverPost.FeatureType = esriBasicOverposterFeatureType.esriOverposterPoint;
                    break;

            }
            ILabelEngineLayerProperties pLabelEngine = new LabelEngineLayerPropertiesClass();
            pLabelEngine.Expression = "[" + fieldname + "]";
            pLabelEngine.Symbol = Symbol;
            pLabelEngine.BasicOverposterLayerProperties = basicoverPost;

            annotLayercol.Add((IAnnotateLayerProperties)pLabelEngine);
            pGeoFeaturelayer.DisplayAnnotation = true;
            axMapControl1.Refresh();
        }

最后调用：

  private void labelFeatureToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //MessageBox.Show(PropertiesForm.FieldName);
            IFeatureLayer layer = axMapControl1.CustomProperty as IFeatureLayer;

            IGeoFeatureLayer pGeoFeaturelayer = layer as IGeoFeatureLayer;
            IAnnotateLayerPropertiesCollection annotLayercol = pGeoFeaturelayer.AnnotationProperties;

            string fieldname = PropertiesForm.FieldName;
            ITextSymbol symbol = PropertiesForm.TextSymbol;

            if (show == false)
            {

                //AddLabel(layer, "XZQMC", symbol);
                Label(layer, fieldname, symbol);
                show = true;
                MessageBox.Show("插入成功！");
            }

            else
            {
                annotLayercol.Clear();
                //container.DeleteAllElements();
                show = false;

                axMapControl1.Refresh();
            }
        }