IPoilygon转IPoint

  private void 河流面转点ToolStripMenuItem_Click(object sender, EventArgs e)
         {
             ESRI.ArcGIS.Geodatabase.IWorkspaceFactory wsf = new ESRI.ArcGIS.DataSourcesFile.ShapefileWorkspaceFactory();
             IWorkspace ws = wsf.OpenFromFile(@"F:\1-水利项目\安徽水利\0826处理", );

             IFeatureClass autoStation = (ws as IFeatureWorkspace).OpenFeatureClass("淮河干流面");
             IFeatureClass f1 = (ws as IFeatureWorkspace).OpenFeatureClass("河道范围点");

             int num = autoStation.FeatureCount(null);
             int k = ;
             string file = @"F:\1-水利项目\安徽水利\ANSL20120808\ANSL\OutPut\淮河干流\hedaopolygon.txt";
             if (File.Exists(file))
             {
                 File.Delete(file);
             }
             StreamWriter writer = new StreamWriter(file, true);
             string strpt = "";
             for (int i = ; i < num; i++)
             {
                 IPolygon pg = autoStation.GetFeature(i).Shape as IPolygon;

                 IPointCollection ptc = pg as IPointCollection;
                 for (int j = ; j < ptc.PointCount; j++)
                 {
                     IPoint pt = ptc.get_Point(j);
                     k++;
                     IFeature fea = f1.CreateFeature();
                     fea.Shape = pt;
                     fea.set_Value(fea.Fields.FindField("Id"), k);
                     fea.set_Value(fea.Fields.FindField("longi"), pt.X);
                     fea.set_Value(fea.Fields.FindField("latit"), pt.Y);
                     fea.Store();

                     strpt=strpt+pt.X+","+pt.Y+","+"0,";
                 }
                 strpt = strpt + ptc.get_Point().X + "，" + ptc.get_Point().Y + "," + "0,";
             }
             writer.Write(strpt);
             writer.Close();
         }

IPolygon转换为IPoint，且点的坐标值写入txt中。