如何创建一个要素数据类 IField，IFieldEdit，IFields，IFieldsEditI，GeometryDef，IGeometryDefEdit接口
如何创建一个要素数据类
创建要素类用到了IFeatureWorkspace.CreateFeatureClass方法，在这个方法中有众多的参数，为了满足这些参数，我们要学习和了解下面的接口.
IField，IFieldEdit，IFields，IFieldsEditI，GeometryDef，IGeometryDefEdit接口
字段对应表中的一列，一个要素类必须有至少2个字段，而多个字段的集合就构成了字段集，在要素类中，有一个特殊的字段，描述了空间对象，我们称之为几何字段，其中GeometryDef是用来设计几何字段的。这个几何字段定义了要素类的类型,比如说我们要在Catalog创建一个点要素类，那么我们必须指定他的类型为Point。
而上面这6个接口，其实是三类，以Edit结尾的接口是可写的，也就是说对字段，字段集合，以及几何字段的编辑都是通过后者完成的。空间数据的一个重要属性就是参考系，参考系也是在GeometryDef中定义的。
注意 在NET中，会遇到以“_2”结尾的属性，这些属性是可写的。
IGeometryDefEdit Interface接口
Members
| Description | ||
|---|---|---|
 |
AvgNumPoints | The estimated average number of points per feature. |
 |
AvgNumPoints | The estimated average number of points per feature. |
|
GeometryType | The enumerated geometry type. |
|
GeometryType | The geometry type. |
|
GridCount | The number of spatial index grids. |
|
GridCount | The number of spatial index grids. |
|
GridSize | The size of a spatial index grid. |
|
GridSize | The size of a spatial index grid. |
|
HasM | Indicates if the feature class has measure (M) values. |
|
HasM | Indicates if the feature class will support M values. |
|
HasZ | Indicates if the feature class will support Z values. |
|
HasZ | Indicates if the featureClass has Z values. |
|
SpatialReference | The spatial reference for the dataset. |
 |
SpatialReference | The spatial reference of the dataset. |
Inherited Interfaces
| Interfaces | Description |
|---|---|
| IGeometryDef | Provides access to members that return information about the geometry definition. |
Classes that implement IGeometryDefEdit
| Classes | Description |
|---|---|
| GeometryDef | ESRI Geometry Definition object. |
//定义一个几何字段，类型为点类型
ISpatialReference pSpatialReference = axMapControl1.ActiveView.FocusMap.SpatialReference; //空间参考系
IGeometryDefEdit pGeoDef = new GeometryDefClass();
IGeometryDefEdit pGeoDefEdit = pGeoDef as IGeometryDefEdit;
pGeoDefEdit.GeometryType_2 = esriGeometryType.esriGeometryPoint;
pGeoDefEdit.SpatialReference_2 = pSpatialReference;
//定义一个字段集合对象
IFields pFields = new FieldsClass();
IFieldsEdit pFieldsEdit = (IFieldsEdit)pFields;
//定义单个的字段
IField pField = new FieldClass();
IFieldEdit pFieldEdit = (IFieldEdit)pField;
pFieldEdit.Name_2 = "SHAPE";
pFieldEdit.Type_2 = esriFieldType.esriFieldTypeGeometry;
pFieldsEdit.AddField(pField);
pFieldEdit.GeometryDef_2 = pGeoDef;
//定义单个的字段，并添加到字段集合中
pField = new FieldClass();
pFieldEdit = (IFieldEdit)pField;
pFieldEdit.Name_2 = "STCD";
pFieldEdit.Type_2 = esriFieldType.esriFieldTypeString;
pFieldsEdit.AddField(pField);
//定义单个的字段，并添加到字段集合中
pField = new FieldClass();
pFieldEdit = (IFieldEdit)pField;
pFieldEdit.Name_2 = "SLM10";
pFieldEdit.Type_2 = esriFieldType.esriFieldTypeString;
pFieldsEdit.AddField(pField);
//定义单个的字段，并添加到字段集合中
pField = new FieldClass();
pFieldEdit = (IFieldEdit)pField;
pFieldEdit.Name_2 = "SLM20";
pFieldEdit.Type_2 = esriFieldType.esriFieldTypeString;
pFieldsEdit.AddField(pField);
//定义单个的字段，并添加到字段集合中
pField = new FieldClass();
pFieldEdit = (IFieldEdit)pField;
pFieldEdit.Name_2 = "SLM40";
pFieldEdit.Type_2 = esriFieldType.esriFieldTypeString;
pFieldsEdit.AddField(pField);
IWorkspaceFactory pFtWsFct = new AccessWorkspaceFactory();
IFeatureWorkspace pWs = pFtWsFct.OpenFromFile(@"E:\arcgis\Engine\s.mdb", 0) as
IFeatureWorkspace;
IFeatureClass pFtClass = pWs.CreateFeatureClass("Test", pFields, null, null,
esriFeatureType.esriFTSimple, "SHAPE", null)
