throw 用來丟擲異常，可自己編寫程式碼，丟擲所需要的異常。

程式碼如下：

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

namespace CheckedAndUnchecked
{
    class Program
    {
        static void Main(string[] args)
        {
            int month;
            string b;

            Console.WriteLine("請輸入月份的值:");
            b = Console.ReadLine();
            month = int.Parse(b);

            switch (month)
            {
                case 1:
                    Console.WriteLine("January");
                    break;
                case 2:
                    Console.WriteLine("Feburary");
                    break;
                case 3:
                    Console.WriteLine("March");
                    break;
                case 4:
                    Console.WriteLine("April");
                    break;
                case 5:
                    Console.WriteLine("May");
                    break;
                case 6:
                    Console.WriteLine("June");
                    break;
                case 7:
                    Console.WriteLine("July");
                    break;
                case 8:
                    Console.WriteLine("August");
                    break;
                case 9:
                    Console.WriteLine("September");
                    break;
                case 10:
                    Console.WriteLine("October");
                    break;
                case 11:
                    Console.WriteLine("Novemer");
                    break;
                case 12:
                    Console.WriteLine("December");
                    break;
                default:
                    throw new ArgumentOutOfRangeException("不存在的月份"); // throw
            }
        }
    }
}
 

輸入 13，則會丟擲異常，執行後輸出結果如下所示：