Arcgis engine 将两个Geometry对象合并为一个新的Geometry对象，其中GeometryA的值会被修改

///
/// </summary>
/// <param name="GeometryA">要合并的一个Geometry</param>
/// <param name="GeometryB">要合并的另一个Geometry</param>
/// <returns>合并后的Geometry</returns>
public static IGeometry UnionTwoGeometries(IGeometry GeometryA, IGeometry GeometryB)
{
ITopologicalOperator pTopologicalOperator = GeometryA as ITopologicalOperator;
IGeometry UnionGeometry = pTopologicalOperator.Union(GeometryB);
return UnionGeometry;
}