public void GetBeamAndColumnSymbols(Document document)
{
    FamilySymbolSet columnTypes = new FamilySymbolSet();
    FamilySymbolSet framingTypes = new FamilySymbolSet();
    FilteredElementCollector collector = new FilteredElementCollector(document);
    ICollection<Element> elements = collector.OfClass(typeof(Family)).ToElements();

    foreach(Element element in elements)
    {
        Family family = element as Family;
        Category category = family.FamilyCategory;
        if (null != category)
        {
            ISet<ElementId> familySymbolIds = family.GetFamilySymbolIds();
            if ((int)BuiltInCategory.OST_StructuralColumns == category.Id.IntegerValue)
            {
                foreach (ElementId id in familySymbolIds)
                {
                    FamilySymbol symbol = family.Document.GetElement(id) as FamilySymbol;
                    columnTypes.Insert(symbol);
                }
            }
            else if ((int)BuiltInCategory.OST_StructuralFraming == category.Id.IntegerValue)
            {
                foreach (ElementId id in familySymbolIds)
                {
                    FamilySymbol symbol = family.Document.GetElement(id) as FamilySymbol;
                    framingTypes.Insert(symbol);
                }
            }
        }
    }

    string message = "Column Types: ";
    FamilySymbolSetIterator fsItor = columnTypes.ForwardIterator();
    fsItor.Reset();
    while (fsItor.MoveNext())
    {
        FamilySymbol familySybmol = fsItor.Current as FamilySymbol;
        message += "\n" + familySybmol.Name;
    }

    TaskDialog.Show("Revit",message);
}

Public Sub GetBeamAndColumnSymbols(document As Document)
    Dim columnTypes As New FamilySymbolSet()
    Dim framingTypes As New FamilySymbolSet()
    Dim collector As New FilteredElementCollector(document)
    Dim elements As ICollection(Of Element) = collector.OfClass(GetType(Family)).ToElements()

    For Each element As Element In elements
        Dim family As Family = TryCast(element, Family)
        Dim category As Category = family.FamilyCategory
        If category IsNot Nothing Then
            Dim familySymbolIds As ISet(Of ElementId) = family.GetFamilySymbolIds()
            If CInt(BuiltInCategory.OST_StructuralColumns) = category.Id.IntegerValue Then
                For Each id As ElementId In familySymbolIds
                    Dim symbol As FamilySymbol = TryCast(family.Document.GetElement(id), FamilySymbol)
                    columnTypes.Insert(symbol)
                Next
            ElseIf CInt(BuiltInCategory.OST_StructuralFraming) = category.Id.IntegerValue Then
                For Each id As ElementId In familySymbolIds
                    Dim symbol As FamilySymbol = TryCast(family.Document.GetElement(id), FamilySymbol)
                    framingTypes.Insert(symbol)
                Next
            End If
        End If
    Next

    Dim message As String = "Column Types: "
    Dim fsItor As FamilySymbolSetIterator = columnTypes.ForwardIterator()
    fsItor.Reset()
    While fsItor.MoveNext()
        Dim familySybmol As FamilySymbol = TryCast(fsItor.Current, FamilySymbol)
        message += vbLf + familySybmol.Name
    End While

    TaskDialog.Show("Revit", message)
End Sub