Program.cs

using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Sheets.v4;
using Google.Apis.Sheets.v4.Data;
using System.Net.Http.Json;

// Models
public class WeatherForecast
{
    public HourlyData Hourly { get; set; }
}

public class HourlyData
{
    public List<string> Time { get; set; }
    public List<double> Temperature_2m { get; set; }
}

class Program
{
    static readonly string[] Scopes = { SheetsService.Scope.Spreadsheets };
    static readonly string ApplicationName = "CSharp Weather to Google Sheets";
    static readonly string SpreadsheetId = "1woc9K7LrfSoTcaby_f__NyTjBPpIaps6LwQHqOXU5Gw"; // your ID
    static readonly string SheetName = "WorkSheet1";

    static async Task Main()
    {
        // --- Step 1: Fetch weather data ---
        using HttpClient client = new();
        string apiUrl = "https://api.open-meteo.com/v1/forecast?latitude=22.28&longitude=114.17&hourly=temperature_2m";
        var forecast = await client.GetFromJsonAsync<WeatherForecast>(apiUrl);

        if (forecast == null || forecast.Hourly?.Time == null) 
        {
            Console.WriteLine("No data retrieved from Open-Meteo.");
            return;
        }

        // --- Step 2: Prepare rows for Sheets ---
        var values = new List<IList<object>>();
        values.Add(new List<object> { "Time", "Temperature (°C)" }); // Header row

        for (int i = 0; i < forecast.Hourly.Time.Count; i++)
        {
            values.Add(new List<object> {
                forecast.Hourly.Time[i],
                forecast.Hourly.Temperature_2m[i]
            });
        }

        // --- Step 3: Connect to Google Sheets ---
        using var stream = new FileStream("credentials.json", FileMode.Open, FileAccess.Read);
        var credential = GoogleCredential.FromStream(stream).CreateScoped(Scopes);

        var service = new SheetsService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = ApplicationName,
        });

        // --- Step 4: Write data ---
        string range = $"{SheetName}!A1";
        var body = new ValueRange { Values = values };

        var request = service.Spreadsheets.Values.Update(body, SpreadsheetId, range);
        request.ValueInputOption = SpreadsheetsResource.ValuesResource.UpdateRequest.ValueInputOptionEnum.USERENTERED;
        var response = await request.ExecuteAsync();

        Console.WriteLine($"✅ Data written to Google Sheets: {response.UpdatedCells} cells updated.");
    }
}