Can we add duplicates to dictionary?

Dictionary<string, Guid> dictLookupLocation = new Dictionary<string, Guid>();

                  
                   QueryExpression locationQuery = new QueryExpression("new_locations");
                   locationQuery.ColumnSet = new ColumnSet(true);
                   EntityCollection locationCollection = CRMHelper.GetCRMService().RetrieveMultiple(locationQuery);

                   foreach (Entity location in locationCollection.Entities)
                   {
                       string locationName = location.GetAttributeValue<string>("new_office");

                       if (!dictLookupLocation.ContainsKey(locationName))
                       {
                           dictLookupLocation .Add(locationName, location.Id);
                       }
                   }