关于mapxtreme +asp.net添加图元 出现的"未将对象引用设置到对象的实例"问题!!求助!!

[wangyafeilina]

以下是我的代码:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using MapInfo.WebControls;
using MapInfo.Mapping;
using MapInfo.Geometry;
using MapInfo.Data;

public partial class _Default : System.Web.UI.Page
{
public MapInfo.Mapping.Map myMap;
private void DrawFeature( )
{
myMap = MapInfo.Engine.Session.Current.MapFactory[this.MapControl1.MapAlias];
//CoordSys coordSys = myMap.GetDisplayCoordSys();
CoordSysFactory factory = MapInfo.Engine.Session.Current.CoordSysFactory;
// create CoordSys objects from srsName
CoordSys coordSys = factory.CreateCoordSys("EPSG:4326");

Feature f = new Feature(new MapInfo.Geometry.Point (coordSys, 0, 0) , new MapInfo.Styles.SimpleVectorPointStyle(35, System.Drawing.Color.Yellow, 10));
// MapInfo.Mapping.FeatureLayer workingLayer = (MapInfo.Mapping.FeatureLayer)myMap.Layers["fea"];
MapInfo.Mapping.FeatureLayer workingLayer = myMap.Layers["fea"] as FeatureLayer;
if (workingLayer != null)
{
workingLayer.Table.InsertFeature(f);
}
}


protected void Page_Load(object sender, EventArgs e)
{

}
protected void Button1_Click(object sender, EventArgs e)
{
DrawFeature();
}
}
以下是报错的内容
“/WebSite2005”应用程序中的服务器错误。
--------------------------------------------------------------------------------

未将对象引用设置到对象的实例。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

源错误:


行 26: Feature f = new Feature(new MapInfo.Geometry.Point (coordSys, 0, 0) , new MapInfo.Styles.SimpleVectorPointStyle(35, System.Drawing.Color.Yellow, 10));
行 27: // MapInfo.Mapping.FeatureLayer workingLayer = (MapInfo.Mapping.FeatureLayer)myMap.Layers["fea"];
行 28: MapInfo.Mapping.FeatureLayer workingLayer = myMap.Layers["fea"] as FeatureLayer;行 29: if (workingLayer != null)
行 30: {


源文件: e:\实验\WebSite2005\Default.aspx.cs 行: 28

堆栈跟踪:


[NullReferenceException: 未将对象引用设置到对象的实例。]
_Default.DrawFeature() in e:\实验\WebSite2005\Default.aspx.cs:28
_Default.Button1_Click(Object sender, EventArgs e) in e:\实验\WebSite2005\Default.aspx.cs:42
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +78
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +101
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2863




--------------------------------------------------------------------------------
版本信息: Microsoft .NET Framework 版本:2.0.50727.3053; ASP.NET 版本:2.0.50727.3053

不知道怎么回事,麻烦大虾帮个忙!

[wjl261333916]

现在想在一张北京区界（只精确到海淀区，朝阳区之类的）的地图上做自己想要的主题图，我的oracle数据库里每条数据都包含具体的地理坐标和某一个属性值的大小（如属性是“quantity”，number类型的），我感觉做主题图要用到数据绑定，就用MapInfo打开bj.tab地图，在里面加了一个“quantity”字段，但在最后绑定时出错，提示：不能 AddColumns.: 无法创建新表。
请问这个问题怎么解决，有人遇过类似问题吗