AutoCAD .NET :: Selecting Entities In Multiple Layers

Is it possible to select entities of multiple layers?

I've looked at... [URL] .....

...and tried the following code.
 
string[] layerNames = {"1", "2", "3"};TypedValue[] tdv = new TypedValue[(layerNames.Length * 3) + 2];int i = 0;tdv[i++] = new TypedValue((int)DxfCode.Operator, "<or");foreach (string ln in layerNames){ tdv[i] = new TypedValue((int)DxfCode.Operator, "<and"); tdv[i + 1] = new TypedValue((int)DxfCode.LayerName, ln); tdv[i + 2] = new TypedValue((int)DxfCode.Operator, "and>"); i += 3;}tdv[i - 2] = new TypedValue((int)DxfCode.Operator, "or>");SelectionFilter sf = new SelectionFilter(tdv);PromptSelectionResult psr = ed.SelectAll(sf);
 This code gives me an error in the PromptSelectionResult.

What would cause the erro?