public static Result<string> DeleteCustomField(string apiKey, string listID, string key)
        {
            CampaignMonitorAPIWrapper.CampaignMonitorAPI.api _api = new CampaignMonitorAPI.api();

            object o = _api.DeleteListCustomField(apiKey, listID, key);

            if (o is CampaignMonitorAPI.Result)
                return new Result<string>((CampaignMonitorAPI.Result)o, "");
            else
                return new Result<string>(0, "Success", Convert.ToString(o));
        }