How to fix CS1061 in .NET MAUI app

Question

I have a CS1061 error in the WeatherViewModel.cs file a .NET MAUI app, which references the NetworkManager.cs. The error is: -

CS1061 'Task<Forecast>' does not contain a definition for 'List' and no accessible extension method 'List' accepting a first argument of type 'Task<Forecast>' could be found (are you missing a using directive or an assembly reference?)

The NetworkManager.cs file and the WeatherViewModel.cs files are shown below: -

NetworkManager.cs file

public class NetworkManager    
{        
public Forecast GetForecast(int id)
        {
            string url = $"http://api.openweathermap.org/data/2.5/forecast?id={id}&units=metric&appid=921e83b9da8a40a760ad74d5cedd6bbd";
            using var httpClient = new HttpClient();
            var request = new HttpRequestMessage(HttpMethod.Get, "http://api.openweathermap.org/data/2.5/weather?id={id}&units=metric&appid=921e83b9da8a40a760ad74d5cedd6bbd");
            string responseJson = string.Empty;
            var response = httpClient.Send(request);
            using var reader = new StreamReader(response.Content.ReadAsStream());
            var responseBody = reader.ReadToEnd();
            using (StreamReader streamReader = new StreamReader(responseBody))
            {
                responseJson = streamReader.ReadToEnd();
            }

            Forecast list = JsonConvert.DeserializeObject<Forecast>(responseJson);

            reader.Close();
            return list;
        }
   }
}

WeatherViewModel.cs file

WeatherViewModel.cs
public WeatherViewModel(City city)   
 {

        networkManager = new NetworkManager();

        ViewModels = new ObservableCollection<IViewModel>() { new DayViewModel(), new WeekViewModel() };

        try

        {

            CurrentWeather currentWeather = networkManager.GetCurrentWeather(city.Id); 

            currentWeather.City = city;

            Forecast = networkManager.GetForecast(city.Id).List; // CS1061 'Task<Forecast>' does not contain a definition for 'List' and no accessible extension method 'List' accepting a first argument of type 'Task<Forecast>' could be found (are you missing a using directive or an assembly reference?)

            BackgroundSource = currentWeather.Weather[0].Icon;

            MainThread.BeginInvokeOnMainThread(() =>

            {

                ViewModels[0].Init(currentWeather);

                ViewModels[1].Init(Forecast);

            });

        }

        catch { }

    }

Answer 1

Hello,

A detailed error resolution of this error code is given in the official C# documentation.

'type' does not contain a definition for 'name' and no accessible extension method 'name' accepting a first argument of type 'type' could be found (are you missing a using directive or an assembly reference?). This error occurs when you try to call a method or access a class member that does not exist.

Please refer to Compiler Error CS1061 for more details.

CS1061 'Task<Forecast>' does not contain a definition for 'List' and no accessible extension method 'List' accepting a first argument of type 'Task<Forecast>' could be found (are you missing a using directive or an assembly reference?)

According to the above error message you provided, Task<Forecast> is not a collection class, so you cannot call List to return a list.

You could replace networkManager.GetForecast(city.Id).List; with networkManager.GetForecast(city.Id).Result;.

Best Regards,

Alec Liu.

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