IPoint从自定义的投影坐标系转换到自定义的地理坐标系

1 IPoint pointStart = new PointClass();
2                     pointStart = xyPolyline.FromPoint;
3 
4                     ISpatialReferenceFactory pSpatialRefFtry = new SpatialReferenceEnvironmentClass();
5                     ISpatialReference fromSpatialRef = pSpatialRefFtry.CreateESRISpatialReferenceFromPRJFile(Application.StartupPath + "\CoordinateSystems\2000_3_Degree_117E.prj");
6                     ISpatialReference toSpatialRef = pSpatialRefFtry.CreateESRISpatialReferenceFromPRJFile(Application.StartupPath + "\CoordinateSystems\China Geodetic Coordinate System 2000.prj");                                    
7                     ISpatialReferenceFactory pSRF = new SpatialReferenceEnvironmentClass();
8                     pointStart.SpatialReference = fromSpatialRef;
9                     pointStart.Project(toSpatialRef);