IWorkspaceFactory pWorkspaceFactory;
IFeatureWorkspace pFeatureWorkspace;
IFeatureLayer pFeatureLayer;
IFeatureDataset pFeatureDataset;
//打开CAD数据集
pWorkspaceFactory = new CadWorkspaceFactoryClass();
pFeatureWorkspace = (IFeatureWorkspace)pWorkspaceFactory.OpenFromFile(directoryPath, 0);
//打开一个要素集
pFeatureDataset = pFeatureWorkspace.OpenFeatureDataset(fileName);
//IFeaturClassContainer可以管理IFeatureDataset中的每个要素类
IFeatureClassContainer pFeatureClassContainer = (IFeatureClassContainer)pFeatureDataset;
//对CAD文件中的要素进行遍历处理
for (int i = 0; i < pFeatureClassContainer.ClassCount - 1; i++)
{
IFeatureClass pFeatureClass = pFeatureClassContainer.get_Class(i);
if (pFeatureClass.FeatureType == esriFeatureType.esriFTAnnotation)
{
//如果是注记，则添加注记层
pFeatureLayer = new CadAnnotationLayerClass();
}
else//如果是点、线、面，则添加要素层
{
pFeatureLayer = new FeatureLayerClass();
pFeatureLayer.Name = pFeatureClass.AliasName;
pFeatureLayer.FeatureClass = pFeatureClass;
this.axmc_Main.Map.AddLayer(pFeatureLayer);
this.axmc_Main.ActiveView.**();
}

}

方法二、直接打开CAD数据的点线面注记等要素类，所加载的数据均为一个独立的图层。

具体代码如下:

   CadWorkspaceFactoryClass fac=new CadWorkspaceFactoryClass ();
   String filePath="E:\cad";
   IFeatureWorkspace space=fac.OpenFromFile(filePath,0) as IFeatureWorkspace ;
   下面是打开FeatureClass的代码：
   //线
   IFeatureClass polyline =space.OpenFeatureClass("NewCAD.dwg:Polyline");  
   IFeatureLayer layer=new CadFeatureLayerClass ();
   layer.FeatureClass =polyline;
   //点
   IFeatureClass point=space.OpenFeatureClass ("NewCAD.dwg:Point");
   layer=new CadFeatureLayerClass ();
   layer.FeatureClass =point;
   //面  
   IFeatureClass polygon=space.OpenFeatureClass ("NewCAD.dwg:Polygon");
   ayer=new CadFeatureLayerClass();
   layer.FeatureClass =polygon;
   //注记  
   IFeatureClass anno=space.OpenFeatureClass ("NewCAD.dwg:Annotation");
   layer=new CadAnnotationLayerClass();
   layer.FeatureClass =anno;
//其实在Coverage文件的开发方式与Autocad方法类似,可以参考.

方法三、利用绘图空间直接加载CAD数据集，加载后各类型数据作为一个图层显示。



IWorkspaceFactory pWorkspaceFactory = new CadWorkspaceFactoryClass();

IWorkspace pWorkspace = pWorkspaceFactory.OpenFromFile(directoryPath, 0);

//--定义一个CAD画图空间，并把上边打开的工作空间赋给它

ICadDrawingWorkspace pCadDrawingWorkspace = pWorkspace as ICadDrawingWorkspace;

//--定义一个CAD的画图数据集，并且打开上边指定的工作空间中一幅CAD图

//--然后赋值给CAD数据集

ICadDrawingDataset pCadDrawingDataset = pCadDrawingWorkspace.OpenCadDrawingDataset(fileName);

//--通过ICadLayer类，把上边得到的CAD数据局赋值给ICadLayer类对象的

//--CadDrawingDataset属性

ICadLayer pCadLayer = new CadLayerClass();

pCadLayer.CadDrawingDataset = pCadDrawingDataset;

//--利用MapControl加载CAD层

this.axmc_Main.Map.AddLayer(pCadLayer);
this.axmc_Main.ActiveView.**();

方法四、也是遍历CAD点线面，但是不用检查数据类型是否为注记。

IWorkspaceFactory pWorkspaceFactory = new CadWorkspaceFactoryClass();
IFeatureWorkspace pFeatureWorkspace = pWorkspaceFactory.OpenFromFile(directoryPath, 0) as IFeatureWorkspace;
IFeatureDataset pFeatureDataset = pFeatureWorkspace.OpenFeatureDataset(fileName);
IFeatureClassContainer pFeatureClassContainer = (IFeatureClassContainer)pFeatureDataset;
for (int i = 0; i < pFeatureClassContainer.ClassCount - 1; i++)
{
IFeatureClass pFeatureClass = pFeatureClassContainer.get_Class(i);
IFeatureLayer pFeatureLayer = new FeatureLayerClass();
pFeatureLayer.FeatureClass = pFeatureClass;
//ICadLayer pCadLayer = new CadLayerClass();
//pCadLayer = pFeatureLayer as ICadLayer;
this.axmc_Main.Map.AddLayer(pFeatureLayer);
this.axmc_Main.ActiveView.**();

}

方法五、类似与方法三。

//Add passed file to MapControl
ICadDrawingDataset pCadDrawingDataset = GetCadDrawingDataset(directoryPath, fileName);
if (pCadDrawingDataset == null) return;
ICadLayer pCadLayer = new CadLayerClass();
pCadLayer.CadDrawingDataset = pCadDrawingDataset;
pCadLayer.Name = fileName;
this.axmc_Main.AddLayer(pCadLayer, 0);

/// <summary>
/// 获取记录集
/// </summary>
/// <param name="directoryPath"></param>
/// <param name="fileName"></param>
/// <returns></returns>
private ICadDrawingDataset GetCadDrawingDataset(string directoryPath, string fileName)
{
//Create a WorkspaceName object
IWorkspaceName pWorkspaceName = new WorkspaceNameClass();
pWorkspaceName.WorkspaceFactoryProgID = "esriDataSourcesFile.CadWorkspaceFactory";
pWorkspaceName.PathName = directoryPath;
//Create a CadDrawingName object
IDatasetName pDatasetName = new CadDrawingNameClass();
pDatasetName.Name = fileName;
pDatasetName.WorkspaceName = pWorkspaceName;
//Open the CAD drawing
IName pName = (IName)pDatasetName;
return (ICadDrawingDataset)pName.Open();
}