Engine中如何对要素类进行投影变换？

【解决办法】：
主要分三步：
1，由于WGS84地理坐标系和西安80投影坐标系的椭球体不同，需要先定义一个地理变换，参考AO帮助链接：
http://resources.arcgis.com/en ... 0.htm
2，获取要素类，遍历每个要素，获取IGeometry，使用IGeometry5.ProjectEx()方法进行投影，将投影后的Geometry重新赋值给Feature，并且报存。
http://resources.arcgis.com/en ... 00000
3，将处理过的要素类的空间参考改为新的空间参考，使用IGeoDatasetSchemaEdit.AlterSpatialReference方法。
http://resources.arcgis.com/en ... 00000

注：如果两个坐标系的椭球体相同的话，直接使用IGeometry5.Project()进行投影即可，也不需要定义地理变换

参考代码（以WGS84到西安80为例）：

IGeographicCoordinateSystem wgs84GCS = createGeographicCoordinateSystem((int)esriSRGeoCSType.esriSRGeoCS_WGS1984);

            IProjectedCoordinateSystem xian80PCS = createProjectedCoordinateSystem((int)esriSRProjCS4Type.esriSRProjCS_Xian1980_3_Degree_GK_CM_102E);

            IGeoTransformation geoTrans = createCustomGeoTrans((ISpatialReference)wgs84GCS, (ISpatialReference)xian80PCS);

            IWorkspace workspace = getWorkspace(esriDataSourcesGDB.FileGDBWorkspaceFactory, @E:\ZhuXinying\testData\Data.gdb);

            IFeatureClass featureClass = openFeatureClass(workspace, WGS841);

            IFeatureCursor featureCur = featureClass.Search(null, false);

            IFeature feature = featureCur.NextFeature();

            while (feature != null)

            {

                IGeometry5 geometry = feature.ShapeCopy as IGeometry5;

                geometry.ProjectEx(xian80PCS as ISpatialReference, esriTransformDirection.esriTransformForward,geoTrans, false, 0, 0);

                feature.Shape = geometry;

                feature.Store();

                feature = featureCur.NextFeature();

            }

            // 定义投影

            defineSpatialReference(featureClass as IDataset, xian80PCS);



​ private void defineSpatialReference(IDataset dataset,ISpatialReference spatialReference)

        {

            IGeoDatasetSchemaEdit geoSchemaEdit = dataset as IGeoDatasetSchemaEdit;

            if (geoSchemaEdit.CanAlterSpatialReference)

            {

                geoSchemaEdit.AlterSpatialReference(spatialReference);

            }

       }

        private IProjectedCoordinateSystem createProjectedCoordinateSystem(int WKID)

        {

            Type factoryType = Type.GetTypeFromProgID(esriGeometry.SpatialReferenceEnvironment);

            System.Object obj = Activator.CreateInstance(factoryType);

            ISpatialReferenceFactory2 pSRF = obj as ISpatialReferenceFactory2;



            // Initialize and create the input and output coordinate systems.

            IProjectedCoordinateSystem pPCS = new ProjectedCoordinateSystemClass();

            pPCS = pSRF.CreateProjectedCoordinateSystem(WKID);

            return pPCS;

        }



        private IGeographicCoordinateSystem createGeographicCoordinateSystem(int WKID)

        {

            Type factoryType = Type.GetTypeFromProgID(esriGeometry.SpatialReferenceEnvironment);

            System.Object obj = Activator.CreateInstance(factoryType);

            ISpatialReferenceFactory2 pSRF = obj as ISpatialReferenceFactory2;

           

            IGeographicCoordinateSystem pGCS = new GeographicCoordinateSystemClass();

            // Initialize and create the input and output coordinate systems.

            pGCS = pSRF.CreateGeographicCoordinateSystem(WKID);

            return pGCS;

        }

        private IGeoTransformation createCustomGeoTrans(ISpatialReference pInputSR, ISpatialReference pOutputSR)

        {

            IGeographicCoordinateSystem pGCSfrom = null;

            IGeographicCoordinateSystem pGCSto = null;

            if (pInputSR is IGeographicCoordinateSystem)

                pGCSfrom = pInputSR as IGeographicCoordinateSystem;

            else if (pInputSR is IProjectedCoordinateSystem)

                pGCSfrom = (pInputSR as IProjectedCoordinateSystem).GeographicCoordinateSystem;

            if (pOutputSR is IGeographicCoordinateSystem)

                pGCSto = pOutputSR as IGeographicCoordinateSystem;

            else if (pOutputSR is IProjectedCoordinateSystem)

                pGCSto = (pOutputSR as IProjectedCoordinateSystem).GeographicCoordinateSystem;

            

            ICoordinateFrameTransformation pCFT = new CoordinateFrameTransformationClass();

            pCFT.PutParameters(p1, p2, p3, p4, p5, p6, p7); //七参数

            pCFT.PutSpatialReferences(pGCSfrom, pGCSto);

            pCFT.Name = Custom GeoTran;

            IGeoTransformation pGeoTrans = pCFT as IGeoTransformation;

            return pGeoTrans;

        }

为什么我用这种方法转换，太慢了？？？？？