AO中一般有两种方式存储图面注记元素，一种使用TextElement，它是文档级的元素，编辑后要通过文档（mxd）保存；另一种是使用Annotation要素类，它是一个独立的要素类（featureclass），需要存储到地理数据库中。使用Annotation featureclass 的方式更灵活、更强大，至于如何灵活，如何强大，待你用到便自知。

1、创建一个标准的Annotation要素类（StandardAnnotationClass）

 1    public AnnotationMark(IFeatureClass outPolygonFc,string mdbPath,int referenceScale)
 2         {
 3             string annotationName = "Annotation";
 4             IWorkspaceFactory workspaceFactory = new AccessWorkspaceFactoryClass();
 5             IFeatureWorkspace featureWorkspace = workspaceFactory.OpenFromFile(mdbPath, 0) as IFeatureWorkspace;
 6             IGeoDataset geoDataset = outPolygonFc as IGeoDataset;
 7             ISpatialReference spatialReference = geoDataset.SpatialReference;
 8             Utils.UserWorkspace.FeatureWorkspace.TryDeleteFeatureClass(annotationName, featureWorkspace);
 9             featureClass = Utils.UserWorkspace.FeatureWorkspace.CreateStandardAnnotationClass(featureWorkspace, null,annotationName, spatialReference, referenceScale, esriUnits.esriMeters, null);
10         }

下面是一个摘自Esri官网的代码段，可以使用它创建StandardAnnotationClass。

值得注意的是：featureDataset根据数据库是否有数据集（dataset）而定，可以是null;referenceScale是注记的参考比例，注记元素会以此为基准，放大或缩小，一般建议设置为出图比例尺，这样所设置的字号即出图字号。configKeyword=""

 1  public static IFeatureClass CreateStandardAnnotationClass(IFeatureWorkspace featureWorkspace, IFeatureDataset featureDataset, String className,
 2 ISpatialReference spatialReference, int referenceScale, esriUnits referenceScaleUnits, String configKeyword)
 3         {
 4             // Create an annotation class and provide it with a name.
 5             ILabelEngineLayerProperties labelEngineLayerProperties = new
 6                 LabelEngineLayerPropertiesClass();
 7             IAnnotateLayerProperties annotateLayerProperties = (IAnnotateLayerProperties)
 8                 labelEngineLayerProperties;
 9             annotateLayerProperties.Class = "Annotation";
10
11             // Get the symbol from the annotation class. Make any changes to its properties
12             // here.
13             ITextSymbol annotationTextSymbol = labelEngineLayerProperties.Symbol;
14             ISymbol annotationSymbol = (ISymbol)annotationTextSymbol;
15
16             // Create a symbol collection and add the default symbol from the
17             // annotation class to the collection. Assign the resulting symbol ID
18             // to the annotation class.
19             ISymbolCollection symbolCollection = new SymbolCollectionClass();
20             ISymbolCollection2 symbolCollection2 = (ISymbolCollection2)symbolCollection;
21             ISymbolIdentifier2 symbolIdentifier2 = null;
22             symbolCollection2.AddSymbol(annotationSymbol, "Annotation", out
23                 symbolIdentifier2);
24             labelEngineLayerProperties.SymbolID = symbolIdentifier2.ID;
25
26             // Add the annotation class to a collection.
27             IAnnotateLayerPropertiesCollection annotateLayerPropsCollection = new
28                 AnnotateLayerPropertiesCollectionClass();
29             annotateLayerPropsCollection.Add(annotateLayerProperties);
30
31             // Create a graphics layer scale object.
32             IGraphicsLayerScale graphicsLayerScale = new GraphicsLayerScaleClass();
33             graphicsLayerScale.ReferenceScale = referenceScale;
34             graphicsLayerScale.Units = referenceScaleUnits;
35
36             // Create the overposter properties for the standard label engine.
37             IOverposterProperties overposterProperties = new BasicOverposterPropertiesClass();
38
39             // Instantiate a class description object.
40             IObjectClassDescription ocDescription = new
41                 AnnotationFeatureClassDescriptionClass();
42             IFeatureClassDescription fcDescription = (IFeatureClassDescription)ocDescription;
43
44             // Get the shape field from the class description‘s required fields.
45             IFields requiredFields = ocDescription.RequiredFields;
46             int shapeFieldIndex = requiredFields.FindField(fcDescription.ShapeFieldName);
47             IField shapeField = requiredFields.get_Field(shapeFieldIndex);
48             IGeometryDef geometryDef = shapeField.GeometryDef;
49             IGeometryDefEdit geometryDefEdit = (IGeometryDefEdit)geometryDef;
50             geometryDefEdit.SpatialReference_2 = spatialReference;
51
52             // Create the annotation layer factory.
53             IAnnotationLayerFactory annotationLayerFactory = new FDOGraphicsLayerFactoryClass();
54
55             // Create the annotation feature class and an annotation layer for it.
56             IAnnotationLayer annotationLayer = annotationLayerFactory.CreateAnnotationLayer
57                 (featureWorkspace, featureDataset, className, geometryDef, null,
58                 annotateLayerPropsCollection, graphicsLayerScale, symbolCollection, false,
59                 false, false, true, overposterProperties, configKeyword);
60
61             // Get the feature class from the feature layer.
62             IFeatureLayer featureLayer = (IFeatureLayer)annotationLayer;
63             IFeatureClass featureClass = featureLayer.FeatureClass;
64
65             return featureClass;
66         }

2、创建Annotation要素（Annotation feature）

上面开始在AnnotationMark类的构造函数中创建了Annotation要素类featureClass，下面是创建Annotation 要素 feature的代码。

博主竟没有在墙内网络上找到相关的实现方案，只得爬墙去攒了这片代码，它主要是使用了ISymbolCollectionElement接口设置了Feature的各种属性。此外，网络上还有使用IFormattedTextSymbol接口的方案，博主并未测试，有需要可以戳下面链接：

Why do these annotations appear stacked/overlapping?（再羡国外论坛生态）

值得注意的是：IGeometry pointGeometry 这个几何对象应该是一个IPoint;esriTextHorizontalAlignment 与 esriTextVerticalAlignment指示这个point在Annotation元素（一个面Polygon）的哪个位置，借此确定放置位置。ISymbolCollectionElement或者IFormattedTextSymbol还有更多的属性可以设置（本文不做补充），这些属性便是该要素记录各字段的值。

 1  public void CreateAnnotationFeature(IGeometry pointGeometry,string text,string fontName,double fontSize,esriTextHorizontalAlignment horizontalAlignment,
 2             esriTextVerticalAlignment verticalAlignment)
 3         {
 4             IFeature feature = featureClass.CreateFeature();
 5
 6             ISymbolCollectionElement symbolCollectionElement = new TextElementClass();
 7             symbolCollectionElement.FontName = fontName;
 8             symbolCollectionElement.Size = fontSize;
 9             symbolCollectionElement.Text = text;
10             symbolCollectionElement.HorizontalAlignment = horizontalAlignment;
11             symbolCollectionElement.VerticalAlignment = verticalAlignment;
12             symbolCollectionElement.Geometry = pointGeometry;
13
14             IElement element = symbolCollectionElement as IElement;
15             IAnnotationFeature2 annotationFeature2 = feature as IAnnotationFeature2;
16             annotationFeature2.Annotation =element;
17             annotationFeature2.Status = esriAnnotationStatus.esriAnnoStatusPlaced;
18             feature.Store();
19         }

3、要素类添加为图层

不啰嗦，上代码：

1           IWorkspaceFactory workspaceFactory = new AccessWorkspaceFactoryClass();
2             IFeatureWorkspace featureWorkspace = workspaceFactory.OpenFromFile(mdbPath, 0) as IFeatureWorkspace;
3             IAnnotationLayerFactory annotationLayerFactory = new FDOGraphicsLayerFactoryClass();
4             IAnnotationLayer annotationLayer = annotationLayerFactory.OpenAnnotationLayer(featureWorkspace, null, "Annotation");
5             ILayer layer_Annotation = annotationLayer as ILayer;
6             layer_Annotation.Name = tfh + "_Annotation";    

原文地址：https://www.cnblogs.com/yzhyingcool/p/11518652.html