Explain code - value vs reference type

protected void Page_Load(object sender, EventArgs e)
		{
			string weather = "rainy";
			ChangeTheString(weather);
			var p = weather; //*** this comes out as "rainy" because string is a reference type so even tho the function changes the value, we'll still get "rainy"

			string[] rainydays = new[] {"Monday", "Friday"};
			ChangeTheArray(rainydays);
			var t = rainydays; //*** this comes out as "Monday" and "Sunday". string array is a value type? (I don't think this is correct even tho I got the answer right)

			Forecast forecast = new Forecast {Temp = 700, Pressure = 20};
			ChangeTheClassInstance(forecast);
			var s = forecast.Temp; //*** this is 35. I got this wrong. I a new instance of Forecast is created and passed. If "class" is a reference type, why didn't I get 700?
		}

		public class Forecast
		{
			public int Temp { get; set; }
			public int Pressure { get; set; }
		}

		public static void ChangeTheString(string weather)
		{
			weather = "sunny";

		}

		public static void ChangeTheArray(string[] rainyDays)
		{
			rainyDays[1] = "Sunday";

		}

		public static void ChangeTheClassInstance(Forecast forecast)
		{
			forecast.Temp = 35;

		}
	}

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