How we can write on C# in Linux: Implementing PanelApplet to Gnome Desktop

using System;
using System.Linq;
using System.Xml.Linq;
using System.Collections.Generic;

using WeatherApplet.Data;

namespace WeatherApplet.Model
{

	public static class WeatherService
	{
		private  static GlobalWeather service = new GlobalWeather();
		private static Dictionary<string, IEnumerable<string>> 
			citiesOfcountry = new Dictionary<string, IEnumerable<string>>();
			
		public static CurrentWeather GetWeather(string country, string city)
		{
			string xml = service.GetWeather(city, country);
			XElement root = XElement.Parse(xml);
			
			return CurrentWeather.Create(root.ToString());
		}
		
		
		public static IEnumerable<string> GetCitiesByCountry(string country)
		{
			if(!citiesOfcountry.ContainsKey(country))
			{
				string xml = service.GetCitiesByCountry(country);
				
				XElement root = XElement.Parse(xml);
								
				citiesOfcountry.Add(country, 
					    (from city in root.Elements()
				         orderby city.Element("City").Value
						 select city.Element("City").Value));
			}
			
			return citiesOfcountry[country];
		}
		
	}
}