using System.Threading; using System.Threading.Tasks; namespace ConsoleApplication { class Program { static void Main() { var radius = 1.0; var area = CalculateCircleAreaAsync(radius).Result; Console.WriteLine(area); // 計算結果を表示 Console.ReadLine(); } static async Task<double> CalculateCircleAreaAsync(double radius) { var π = await Task.Run(() => { Thread.Sleep(3000); return Math.PI; // 級数展開などで円周率を計