Take a look at Environment

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CLRviaCsharp_00
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Is64BitOperationSystem: {0}", Environment.Is64BitOperatingSystem ? "在64位Windows上运行" : "不在64位Windows上运行");
            Console.WriteLine("Is64BitProcess: {0}", Environment.Is64BitProcess ? "在64位地址空间中运行" : "不在64位地址空间中运行");
            Console.ReadKey();
        }
    }
}