c#删除属性

<P>   ILayer ler=this.axMapControl1 .Map .get_Layer (0);<BR>   IFeatureLayer fler=(IFeatureLayer)ler;<BR>   IFeatureClass pLayerclass=fler.FeatureClass ;<BR>   int a=pLayerclass.Fields.FindField ("说明"); <BR>   IFields pfields;<BR>   pfields=pLayerclass.Fields ;<BR>   IField field=pfields.get_Field (a);<BR>   pLayerclass.DeleteField (field);<BR>   MessageBox.Show ("删除成功");</P>
<P>但是提示如下：</P>
<P>DBMS table not found[Microsoft OLE DB Provider for SQL Server: 无法更改表 '供电_高压设备'，因为数据库 'sde' 中不存在此表。]</P>
<P>这是怎么回事呢？</P>
<P>另外采用下面的代码也是同样的问题</P>
<P>pLayerclass为通过IFeatureWorkspace打开的IFeatureClass</P>
<P>int a=pLayerclass.Fields.FindField (this.textBox1 .Text .ToString ()); <BR>     IFields pfields;<BR>     pfields=pLayerclass.Fields ;<BR>     pfields.get_Field (a);<BR>     IField field=pfields.get_Field (a);<BR>     pLayerclass.DeleteField (field);<BR>     MessageBox.Show ("删除成功");</P>