public async Task <List <RootObject> > GetHistoricalWeatherAsync(string location, DateTime startDate, int duration) { var dateOneYearAgo = startDate.AddYears(-1); var oneYearAgo = await _weatherClient.GetHistoricalWeatherDataAsync(location, dateOneYearAgo, duration); var dateTwoYearsAgo = startDate.AddYears(-2); var twoYearsAgo = await _weatherClient.GetHistoricalWeatherDataAsync(location, dateTwoYearsAgo, duration); var dateThreeYearsAgo = startDate.AddYears(-3); var threeYearsAgo = await _weatherClient.GetHistoricalWeatherDataAsync(location, dateThreeYearsAgo, duration); List <RootObject> items = new List <RootObject> { oneYearAgo, twoYearsAgo, threeYearsAgo }; return(items); }