GetAll3 Method returns empty values (API C#)

Hello everybody, 

I'm trying to read the document specific properties of components in an assambly. 

Unfortunately I get back an array of values containing all empty strings (values are not empty) while the property names work pretty well and are correct. 

Here is the code I wrote:

ISldWorks app = getSwApp();
IModelDoc2 model = app.IActiveDoc2;
IModelDocExtension ext = model.Extension;
IAssemblyDoc asm = model as IAssemblyDoc;
if (asm != null)
{
    object[] comps = (object[])asm.GetComponents(true);
    IComponent2 comp = (IComponent2)comps[0] 
    ICustomPropertyManager swCustProp = comp.get_CustomPropertyManager("");
    object names = null;
    object types = null;
    object values = null;
    object reso = null;
    object propl = null;
    int result = swCustProp.GetAll3(ref names, ref types, ref values, ref reso, ref propl);
}

Thanks in advance.

Best wishes,

Tom