arcengine路径分析，类型无法隐式转换，该怎么改？

if (IfLayerExist("NetworkDataset") == false)
{
ILayer layer;
INetworkLayer networkLayer = new NetworkLayer();
networkLayer.NetworkDataset = networkDataset;
layer = networkLayer as ILayer;
layer.Name = "NetworkDataset";
m_hookHelper.ActiveView.FocusMap.AddLayer(layer);
layer.Visible = false;
}

那就先定义一个NetworkLayer，再显示强转成INetworkLayer试试