C#AE二次开发打开CAD文件

using (openFileDialog = new OpenFileDialog())
            {
                openFileDialog.Title = "打开CAD文件";
                openFileDialog.Filter = "(*.dwg)|*.dwg";
                if (openFileDialog.ShowDialog() == DialogResult.OK)
                {
                    openFullPath = openFileDialog.FileName;
                    fileName = System.IO.Path.GetFileName(openFullPath);
                    openPath = System.IO.Path.GetDirectoryName(openFullPath);
                    if (openPath == null) return;
                    IWorkspaceName pWorkspaceName = new WorkspaceNameClass();
                    pWorkspaceName.WorkspaceFactoryProgID = "esriDataSourcesFile.CadWorkspaceFactory";
                    pWorkspaceName.PathName = openPath;
                    //Create a CadDrawingName object
                    IDatasetName pDatasetName = new CadDrawingNameClass();
                    pDatasetName.Name = fileName;
                    pDatasetName.WorkspaceName = pWorkspaceName;
                    //Open the CAD drawing
                    IName pName = (IName)pDatasetName;
                    ICadDrawingDataset pCadDrawingDataset = (ICadDrawingDataset)pName.Open();
                    if (pCadDrawingDataset == null) return;
                    ICadLayer pCadLayer = new CadLayerClass();
                    pCadLayer.CadDrawingDataset = pCadDrawingDataset;
                    pCadLayer.Name = fileName;
                    axMapControl1.AddLayer(pCadLayer);
                }
            }