急急，当拷贝一个要素时，为什么在vb.net中会出错，而在VB中不出错？
private sub copyAttribute(byref pTargetClass as IFeatureClass,byval pSourceFeature as IFeature)
Dim i As Long
Dim lValueIndex As Long
Dim lNewIndex As Long
Dim pBuffer As IFeatureBuffer
Dim pInsert As IFeatureCursor
Set pInsert = pTargetClass.Insert(True)

Set pBuffer = pTargetClass.CreateFeatureBuffer
pBuffer.Shape = pSourceFeature.ShapeCopy

For i = 0 To pSourceFeature.Fields.FieldCount - 1
If ((pSourceFeature.Fields.Field(i).Type <> esriFieldTypeOID) And _
(pSourceFeature.Fields.Field(i).Type <> esriFieldTypeGeometry)) Then
lValueIndex = pSourceFeature.Fields.FindField(pSourceFeature.Fields.Field(i).Name)
lNewIndex = pBuffer.Fields.FindField(pSourceFeature.Fields.Field(i).Name)

pBuffer.Value(lNewIndex) = pFeature.Value(lValueIndex) '当某些字段值为空时，出错
End If
Next i

pInsert.InsertFeature pBuffer

pInsert.Flush

end sub

[解决办法]
可以用IIf函数做个判断阿
pBuffer.Value(lNewIndex) =IIf (pFeature.Value(lValueIndex) is null or pFeature.Value(lValueIndex) = "" ,null,pFeature.Value(lValueIndex) )