decimal GetMaterialCost()
{
var materials = new List<Material>();
Services.Clear();
foreach (var service in _entryDictionary.Keys)
{
Services.Add(service);
if (service.Materials == null)
{
service.Materials = new ObservableCollection<Material>();
}
foreach (var material in service.Materials)
{
materials.Add(material);
}
}
return materials.Cost();
}