Creating and accessing layer filter information

By Balaji Ramamoorthy

Here is a ObjectARX and .Net sample code to create and access the layer filters. A simple trick to know the layer filter expression that will suit your needs, is to create a layer filter in AutoCAD and use this code to find the filter expression for it. This can then be used in your code to create a new layer filter.

Using ObjectARX :

Acad::ErrorStatus es = Acad::eOk;
AcDbDatabase *pDb = 
             acdbHostApplicationServices()->workingDatabase();
 
AcLyLayerFilterManager *pLayerFilterManager = 
                               aclyGetLayerFilterManager(pDb);
 
AcLyLayerFilter *pRoot = NULL;
AcLyLayerFilter *pCurrent = NULL;
es = pLayerFilterManager->getFilters(pRoot, pCurrent);
if(es != Acad::eOk)
    return;
 
if(pRoot != NULL)
{
    AcArray filters;
    filters = pRoot->getNestedFilters();
 
    // Lets find out about the root filter
    acutPrintf
            (
                ACRX_T("n(Root) Name : %s Expr : %s"), 
                pRoot->name(), 
                pRoot->filterExpression()
            );
 
    // Lets find out about all the filters
    for(int i=0; i < filters.length();i++)
    {
        acutPrintf
                (
                    ACRX_T("nName : %s Expr : %s"), 
                    filters.at(i)->name(), 
                    filters.at(i)->filterExpression()
                );
    }
 
    // Lets find out about the current filter
    if(pCurrent != NULL)
    {
        acutPrintf
                (
                    ACRX_T("n(Current) Name : %s Expr : %s"), 
                    pCurrent->name(), 
                    pCurrent->filterExpression()
                );
    }
 
    // Create and add a new layer filter
    AcLyLayerFilter *pMyLyFilter = new AcLyLayerFilter();
    pMyLyFilter->setName(ACRX_T("MyLyFilter"));
    pMyLyFilter->setFilterExpression(ACRX_T("NAME == "*Test*""));
 
    es = pRoot->addNested(pMyLyFilter);
    es = pLayerFilterManager->setFilters(pRoot, pMyLyFilter);
 
    delete pRoot;
}

Using AutoCAD .Net API :

using Autodesk.AutoCAD.LayerManager;

[CommandMethod("CreateLayerFilter")]
public void CreateLayerFilter()
{
    Document doc 
                = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    Editor ed = doc.Editor;
 
    LayerFilterTree filterTree = db.LayerFilters;
    LayerFilterCollection filters 
                            = filterTree.Root.NestedFilters; 
 
    // Lets find out about the root filter
    ed.WriteMessage
            (
                String.Format("n(Root) Name : {0} Expr : {1}", 
                db.LayerFilters.Root.Name, 
                db.LayerFilters.Root.FilterExpression)
            );
 
    // Lets find out about all the filters
    foreach(LayerFilter f in filters)
    {
        ed.WriteMessage
                (
                    String.Format("nName : {0} Expr : {1}", 
                    f.Name, 
                    f.FilterExpression)
                );
    }
 
    // Lets find out about the current filter
    if(db.LayerFilters.Current != null)
    {
        ed.WriteMessage
        (
            String.Format("n(Current) Name : {0} Expr : {1}", 
            db.LayerFilters.Current.Name, 
            db.LayerFilters.Current.FilterExpression)
        );
    }
 
    // Create and add a new layer filter
    LayerFilter layerFilter = new LayerFilter();
    layerFilter.Name = "MyLyFilter";
    layerFilter.FilterExpression = "NAME == "*Test*"";
    filters.Add(layerFilter);
 
    // Set the changed layer filters tree to the database
    db.LayerFilters = filterTree;
}