Points

    一个点包括X、Y坐标，同时可以增加M、Z值及ID属性来扩展点的功能。

    Multipoints

    点的集合，多点组成Multipoint几何类型，使用multipoint对象实现了的IPointCollection接口可以访问所有的点元素，这些点同样可以拥有M、Z值及ID属性来获得更多的地理空间内涵。

    下面列举一个例子，通过一个已知的polyline来定义一个新的multipart polyline。

public IPolyline ConstructMultiPartPolyline(IPolyline inputPolyline)
...{
    IGeometry outGeometry = new PolylineClass();

    //Always associate new, top-level geometries with an appropriate spatial reference.
    outGeometry.SpatialReference = inputPolyline.SpatialReference;

    IGeometryCollection geometryCollection = outGeometry as IGeometryCollection;

    ISegmentCollection segmentCollection = inputPolyline as ISegmentCollection;

    //Iterate over existing polyline segments using a segment enumerator.
    IEnumSegment segments = segmentCollection.EnumSegments;

    ISegment currentSegment;
    int partIndex = 0;;
    int segmentIndex = 0;;
    segments.Next(out currentSegment,ref partIndex, ref segmentIndex);
    while(currentSegment != null)
    ...{
        ILine normal = new LineClass();

        //Geometry methods with _Query_ in their name expect to modify existing geometries.
        //In this case, the QueryNormal method modifies an existing line
        //segment (normal) to be the normal vector to
        //currentSegment at the specified location along currentSegment.
        currentSegment.QueryNormal(esriSegmentExtension.esriNoExtension, 0.5, true, currentSegment.Length / 3, normal);

        //Since each normal vector is not connected to others, create a new path for each one.
        ISegmentCollection newPath = new PathClass();
        object missing = Type.Missing;
        newPath.AddSegment(normal as ISegment, ref missing, ref missing);
        //The spatial reference associated with geometryCollection will be assigned to all incoming paths and segments.
        geometryCollection.AddGeometry(newPath as IGeometry, ref missing, ref missing);

        segments.Next(out currentSegment,ref partIndex, ref segmentIndex);
    }
    //The geometryCollection now contains the new, multipart polyline.
    return geometryCollection as IPolyline;
}

ISegment接口的QueryNormal方法用来在弧段上的某一点生成该弧段的法线，指定其长度，这样就生成了新的segment，并且多个path添加到geometryCollection中，以IPolyline的形式返回。
Polylines

    Polylines是有序path组成的集合，可以拥有M、Z和ID属性值。Polyline对象的IPointCollection接口包含了所有节点的复制，IGeometryCollection接口可以获取polyline的paths，ISegmentCollection接口可以获取 polyline的segments。

    Polyline结构图

    Polygons

    Polygon是一系列rings组成的集合，可以拥有M、Z和ID属性值。每一个ring由一个或多个segment组成，Polygon或ring对象的IPointCollection接口包含了所有节点的复制，IGeometryCollection接口可以获取polygon的rings， ISegmentCollection接口可以获取polygon的segments。

    Polygon结构图