Dotspatial 图层添加字段和删除字段

//===============图层添加字段
polygonFeatureSet = (FeatureSet)mapMain.Layers[0].DataSet;
polygonFeatureSet.Projection = mapMain.Projection;
polygonFeatureSet.FeatureType = FeatureType.Polygon;
DataColumn column = new DataColumn("IDxx", typeof(int));
if (!polygonFeatureSet.DataTable.Columns.Contains("IDxx"))
{
　　polygonFeatureSet.DataTable.Columns.Add(column);
}
polygonFeatureSet.Save();

//==============图层删除字段
if (mapMain.Layers.Count > 0)
{
　　MapPolygonLayer polygonLayer = default(MapPolygonLayer);
　　polygonLayer = (MapPolygonLayer)mapMain.Layers[0];
　　if (polygonLayer == null)
　　{
　　　　MessageBox.Show("The layer is not a polygon layer.");
　　}
　　else
　　{
　　　　polygonLayer.DataSet.DataTable.Columns.Remove("IDxx");
　　　　polygonLayer.DataSet.Save();
　　　　dataGridView1.DataSource = polygonLayer.DataSet.DataTable;
　　}
}
else
{
　　MessageBox.Show("Please add a layer to the map.");
}