MapXtreme 更新点，如果点不存在，创建

许多网文谈到移动点有二种办法，一是删除后建立，二是通过前后点的偏移。

经过试验发现，可以采用更新坐标点的办法，实现点的移动，其他图元以此类推。（在MapXtreme 6.8下测试通过）

// 更新点，如果点不存在，则创建
public void UpdatePoint(string tableName, string ID, DPoint dPoint, short pCode, int pSize, Color color, string myLabel)
{
    MapInfo.Mapping.Map myMap = MapInfo.Engine.Session.Current.MapFactory[mapControl1.Map.Alias];
    FeatureLayer workLayer = (MapInfo.Mapping.FeatureLayer)myMap.Layers[tableName + "层"];
    MapInfo.Data.Table table = workLayer.Table;

    FeatureGeometry point = new MapInfo.Geometry.Point(workLayer.CoordSys, dPoint);

    SearchInfo si = MapInfo.Data.SearchInfoFactory.SearchWhere("type='点' and index=" + "'" + ID + "'");
    Feature feature = MapInfo.Engine.Session.Current.Catalog.SearchForFeature(table, si);
    if (feature == null)
    {
        SimpleVectorPointStyle spsPoint = new MapInfo.Styles.SimpleVectorPointStyle(pCode, color, pSize);
        CompositeStyle pointStyle = new MapInfo.Styles.CompositeStyle(spsPoint);
        
        Feature pointRow = new MapInfo.Data.Feature(table.TableInfo.Columns);
        pointRow.Geometry = point;
        pointRow.Style = pointStyle;

        pointRow["type"] = "点";
        pointRow["index"] = ID;
        pointRow["value"] = myLabel;
        table.InsertFeature(pointRow);
    }
    else
    {
        feature.Geometry = point;
        feature["value"] = myLabel;
        feature.Update();
    }
}