public void GetBeamAndColumnSymbols(Document document)
{
   List<FamilySymbol> columnTypes = new List<FamilySymbol>();
   List<FamilySymbol> framingTypes = new List<FamilySymbol>();
    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 (BuiltInCategory.OST_StructuralColumns == category.BuiltInCategory)
            {
                foreach (ElementId id in familySymbolIds)
                {
                    FamilySymbol symbol = family.Document.GetElement(id) as FamilySymbol;
                    columnTypes.Add(symbol);
                }
            }
            else if (BuiltInCategory.OST_StructuralFraming == category.BuiltInCategory)
            {
                foreach (ElementId id in familySymbolIds)
                {
                    FamilySymbol symbol = family.Document.GetElement(id) as FamilySymbol;
                    framingTypes.Add(symbol);
                }
            }
        }
    }

    string message = "Column Types: ";
    foreach (FamilySymbol familySymbol in columnTypes)
    {
       message += "\n" + familySymbol.Name;
    }

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

Public Sub GetBeamAndColumnSymbols(document As Document)
   Dim columnTypes As New System.Collections.Generic.List(Of FamilySymbol)
   Dim framingTypes As New System.Collections.Generic.List(Of FamilySymbol)
   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 BuiltInCategory.OST_StructuralColumns = category.BuiltInCategory Then
            For Each id As ElementId In familySymbolIds
               Dim symbol As FamilySymbol = TryCast(family.Document.GetElement(id), FamilySymbol)
               columnTypes.Add(symbol)
            Next
         ElseIf BuiltInCategory.OST_StructuralFraming = category.BuiltInCategory Then
            For Each id As ElementId In familySymbolIds
               Dim symbol As FamilySymbol = TryCast(family.Document.GetElement(id), FamilySymbol)
               framingTypes.Add(symbol)
            Next
         End If
      End If
   Next

   Dim message As String = "Column Types: "
   For Each familySybmol As FamilySymbol In columnTypes
      message += vbLf + familySybmol.Name
   Next

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