//引入命名空间
using System;

public class Example
{
   public static void Main()
   {
      Tuple<string, Nullable<int>>[] scores = 
                    { new Tuple<string, Nullable<int>>("Jack", 78),
                      new Tuple<string, Nullable<int>>("Abbey", 92), 
                      new Tuple<string, Nullable<int>>("Dave", 88),
                      new Tuple<string, Nullable<int>>("Sam", 91), 
                      new Tuple<string, Nullable<int>>("Ed", null),
                      new Tuple<string, Nullable<int>>("Penelope", 82),
                      new Tuple<string, Nullable<int>>("Linda", 99),
                      new Tuple<string, Nullable<int>>("Judith", 84) };
      int number;
      double mean = ComputeMean(scores, out number);
      Console.WriteLine("Average test score: {0:N2} (n={1})", mean, number);
   }

   private static double ComputeMean(Tuple<string, Nullable<int>>[] scores, out int n) 
   {
      n = 0;      
      int sum = 0;
      foreach (var score in scores)
      {
         if (score.Item2.HasValue)
         { 
            n += 1;
            sum += score.Item2.Value;
         }
      }     
      if (n > 0)
         return sum / (double) n;
      else
         return 0;
   }
}

//引入命名空间
using System;

public class Class1
{
   public static void Main()
   {
      int dividend, divisor;
      Tuple<int, int> result;
      
      dividend = 136945; divisor = 178;
      result = IntegerDivide(dividend, divisor);
      if (result != null)
         Console.WriteLine(@"{0} \ {1} = {2}, remainder {3}", 
                           dividend, divisor, result.Item1, result.Item2);
      else
         Console.WriteLine(@"{0} \ {1} = <Error>", dividend, divisor);
                        
      dividend = Int32.MaxValue; divisor = -2073;
      result = IntegerDivide(dividend, divisor);
      if (result != null)
         Console.WriteLine(@"{0} \ {1} = {2}, remainder {3}", 
                           dividend, divisor, result.Item1, result.Item2);
      else
         Console.WriteLine(@"{0} \ {1} = <Error>", dividend, divisor);
   }

   private static Tuple<int, int> IntegerDivide(int dividend, int divisor)
   {
      try {
         int remainder;
         int quotient = Math.DivRem(dividend, divisor, out remainder);
         return new Tuple<int, int>(quotient, remainder);
      }   
      catch (DivideByZeroException) {
         return null;
      }      
   }
}