ex-18-10

Programming Csharp Source Code(代码) Programming Csharp Source Code

// Example 18-10: Dynamic invocation with interfaces

namespace Programming_CSharp
{
   using System;
   using System.Diagnostics;
   using System.IO;
   using System.Reflection;

   // used to benchmark the looping approach
   public class MyMath
   {
      // sum numbers with a loop
      public int DoSumLooping(int initialVal)
      {
         int result = 0;
         for(int i = 1;i <=initialVal;i++)
         {
            result += i;
         }
         return result;
      }
   }

   public interface IComputer
   {
      double ComputeSum();
   }

   // responsible for creating the BruteForceSums
   // class and compiling it and invoking the
   // DoSums method dynamically
   public class ReflectionTest
   {
      // the public method called by the driver
      public double DoSum(int theValue)
      {
         if (theComputer == null)
         {
            GenerateCode(theValue);
         }
         return (theComputer.ComputeSum());
      }

      // generate the code and compile it
      private void GenerateCode(int theVal)
      {
         // open the file for writing
         string fileName = "BruteForceSums";
         Stream s = 
            File.Open(fileName + ".cs", FileMode.Create);
            StreamWriter wrtr = new StreamWriter(s);
            wrtr.WriteLine(
            "// Dynamically created BruteForceSums class");

         // create the class
         string className = "BruteForceSums";
         wrtr.WriteLine(
            "class {0} : Programming_CSharp.IComputer ", 
            className);
         wrtr.WriteLine("{");

         // create the method
         wrtr.WriteLine("\tpublic double ComputeSum()");
         wrtr.WriteLine("\t{");
         wrtr.WriteLine("\t// Brute force sum method");
         wrtr.WriteLine("\t// For value = {0}", theVal);

         // write the brute force additions
         wrtr.Write("\treturn 0");
         for (int i = 1;i<=theVal;i++)
         {
            wrtr.Write("+ {0}",i);
         }
         wrtr.WriteLine(";");    // finish method
         wrtr.WriteLine("\t}");    // end method
         wrtr.WriteLine("}");    // end class

         // close the writer and the stream
         wrtr.Close();
         s.Close();

         // Build the file
         ProcessStartInfo psi = 
            new ProcessStartInfo();
         psi.FileName = "cmd.exe";

         string compileString = "/c csc /optimize+ ";
         compileString += "/r:\"Reflection.exe\" ";
         compileString += "/target:library ";
         compileString += "{0}.cs > compile.out";

         psi.Arguments = 
            String.Format(compileString, fileName);
         psi.WindowStyle = ProcessWindowStyle.Minimized;

         Process proc = Process.Start(psi);
         proc.WaitForExit();    // wait at most 2 seconds

         // Open the file, and get a 
         // pointer to the method info
         Assembly a = 
            Assembly.LoadFrom(fileName + ".dll");
         theComputer = (IComputer)  a.CreateInstance(className);
         File.Delete(fileName + ".cs");  // clean up
      }
      IComputer theComputer = null;
   }

   public class TestDriver
   {
      public static void Main()
      {
         const int val = 200;  // 1..200
         const int iterations = 100000;
         double result = 0;

         // run the benchmark
         MyMath m = new MyMath(); 
         DateTime startTime = DateTime.Now;            
         for (int i = 0;i < iterations;i++)
         {
            result = m.DoSumLooping(val);
         }
         TimeSpan elapsed = 
            DateTime.Now - startTime;
         Console.WriteLine(
            "Sum of ({0}) = {1}",val, result);
         Console.WriteLine(
            "Looping. Elapsed milliseconds: " + 
            elapsed.TotalMilliseconds + 
            " for {0} iterations", iterations);

         // run our reflection alternative
         ReflectionTest t = new ReflectionTest();

         startTime = DateTime.Now; 
         for (int i = 0;i < iterations;i++)
         {
            result = t.DoSum(val);
         }

         elapsed = DateTime.Now - startTime;
         Console.WriteLine(
            "Sum of ({0}) = {1}",val, result);
         Console.WriteLine(
            "Brute Force. Elapsed milliseconds: " + 
            elapsed.TotalMilliseconds  + 
            " for {0} iterations", iterations);
      }
   }
}