C# In Depth: Chapter 6

diff --git a/CSharpInDepth/Chapter6/Chapter6.userprefs b/CSharpInDepth/Chapter6/Chapter6.userprefs
index 2147a1e..4e1c5cc 100644 (file)
--- a/CSharpInDepth/Chapter6/Chapter6.userprefs
+++ b/CSharpInDepth/Chapter6/Chapter6.userprefs
@@ -2,7 +2,7 @@
   <MonoDevelop.Ide.Workspace ActiveConfiguration="Debug|x86" />
   <MonoDevelop.Ide.Workbench ActiveDocument="Chapter6/Main.cs">
     <Files>
-      <File FileName="Chapter6/Main.cs" Line="58" Column="45" />
+      <File FileName="Chapter6/Main.cs" Line="94" Column="4" />
     </Files>
   </MonoDevelop.Ide.Workbench>
   <MonoDevelop.Ide.DebuggingService.Breakpoints>

diff --git a/CSharpInDepth/Chapter6/Chapter6/Main.cs b/CSharpInDepth/Chapter6/Chapter6/Main.cs
index bbd61f5..7212898 100644 (file)
--- a/CSharpInDepth/Chapter6/Chapter6/Main.cs
+++ b/CSharpInDepth/Chapter6/Chapter6/Main.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Threading;
+using System.IO;
 
 namespace Chapter6
 {
@@ -16,14 +18,13 @@ namespace Chapter6
                         * Listings 6.1 and 6.2 Skeleton of th new collection type, with no iterator implementation.
                         */
                        object[] values = {"a", "b", "c", "d", "e"};
-                       IterationSampleBad badCollection = new IterationSampleBad(values, 3);
+                       IterationSampleBad badCollection = new IterationSampleBad (values, 3);
                        try {
-                               foreach(object x in badCollection)
-                               {
-                                       Console.WriteLine(x);
+                               foreach (object x in badCollection) {
+                                       Console.WriteLine (x);
                                }
-                       } catch(NotImplementedException e) {
-                               Console.WriteLine("Listings 6.1 and 6.2 exception: {0}", e);
+                       } catch (NotImplementedException e) {
+                               Console.WriteLine ("Listings 6.1 and 6.2 exception: {0}", e);
                        }
 
 
@@ -31,10 +32,9 @@ namespace Chapter6
                         * 
                         * Listings 6.3 Nested class implementing the collection's iterator.
                         */
-                       IterationSample collection = new IterationSample(values, 3);
-                       foreach(object x in collection)
-                       {
-                               Console.WriteLine(x);
+                       IterationSample collection = new IterationSample (values, 3);
+                       foreach (object x in collection) {
+                               Console.WriteLine (x);
                        }
 
 
@@ -42,10 +42,9 @@ namespace Chapter6
                         * 
                         * Listings 6.4 Iterating through the sample collection with C# 2 and yield return.
                         */
-                       IterationSampleYield yieldCollection = new IterationSampleYield(values, 3);
-                       foreach(object x in yieldCollection)
-                       {
-                               Console.WriteLine(x);
+                       IterationSampleYield yieldCollection = new IterationSampleYield (values, 3);
+                       foreach (object x in yieldCollection) {
+                               Console.WriteLine (x);
                        }
 
 
@@ -53,9 +52,68 @@ namespace Chapter6
                         * 
                         * Listings 6.5 Showing the sequence of calls between an iterator and its caller.
                         */
-                       IEnumerable<int> iterable = CreateEnumerable();
-                       IEnumerator<int> iterator = iterable.GetEnumerator();
-                       Console.WriteLine("Starting to iterate");
+                       IEnumerable<int> iterable = CreateEnumerable ();
+                       IEnumerator<int> iterator = iterable.GetEnumerator ();
+                       Console.WriteLine ("Starting to iterate");
+                       while (true) {
+                               Console.WriteLine ("Calling MoveNext()...");
+                               bool result = iterator.MoveNext ();
+                               Console.WriteLine ("... MoveNext result={0}", result);
+                               if (!result) {
+                                       break;
+                               }
+                               Console.WriteLine ("Fetching Current...");
+                               Console.WriteLine ("... Current result={0}", iterator.Current);
+                       }
+
+                       IEnumerable<string> stringIterable = CreateStringEnumerable ();
+                       IEnumerator<string> stringIterator = stringIterable.GetEnumerator ();
+                       Console.WriteLine ("Starting to iterate");
+                       while (true) {
+                               Console.WriteLine ("Calling MoveNext()...");
+                               bool result = stringIterator.MoveNext ();
+                               Console.WriteLine ("... MoveNext result={0}", result);
+                               if (!result) {
+                                       break;
+                               }
+                               Console.WriteLine ("Fetching Current...");
+                               Console.WriteLine ("... Current result={0}", stringIterator.Current);
+                       }
+
+
+                       /**
+                        * 
+                        * Listings 6.6 Demonstration of yield break.
+                        */
+                       DateTime stop = DateTime.Now.AddSeconds (2);
+                       foreach (int i in CountWithTimeLimit(stop)) {
+                               Console.WriteLine ("Received {0}", i);
+                               Thread.Sleep (300);
+                       }
+
+
+                       /**
+                        * 
+                        * Listings 6.8 Looping over the lines in a file using an iterator block.
+                        */
+                       foreach (string line in ReadLines ("TheLayofLeithian.txt")) {
+                               Console.WriteLine(line);
+                       }
+
+
+                       /**
+                        * 
+                        * Listings 6.7 Demonstration of yield break working with try/finally.
+                        */
+                       DateTime stopFinally = DateTime.Now.AddSeconds (2);
+                       foreach (int i in CountWithTimeLimitFinally(stopFinally)) {
+                               Console.WriteLine ("Received {0}", i);
+                               if (i > 3) {
+                                       Console.WriteLine ("Returning");
+                                       return;
+                               }
+                               Thread.Sleep (300);
+                       }
                }
 
                static IEnumerable<int> CreateEnumerable ()
@@ -73,6 +131,60 @@ namespace Chapter6
 
                        Console.WriteLine("{0}End of CreateEnumerable()", Padding);
                }
+
+               static IEnumerable<string> CreateStringEnumerable ()
+               {
+                       string[] values = {"a", "b", "c"};
+                       Console.WriteLine ("{0}Start of CreateStringEnumerable()", Padding);
+
+                       for (int i=0; i < 3; i++) {
+                               Console.WriteLine("{0}About to yield {1}", Padding, values[i]);
+                               yield return values[i];
+                               Console.WriteLine("{0}After yield", Padding);
+                       }
+
+                       Console.WriteLine("{0}Yielding final value", Padding);
+                       yield return null;
+
+                       Console.WriteLine("{0}End of CreateStringEnumerable()", Padding);
+               }
+
+               static IEnumerable<int> CountWithTimeLimit (DateTime limit)
+               {
+                       for (int i = 1; i <= 100; i++) {
+                               if (DateTime.Now >= limit)
+                               {
+                                       yield break;
+                               }
+                               yield return i;
+                       }
+               }
+
+               static IEnumerable<int> CountWithTimeLimitFinally (DateTime limit)
+               {
+                       try {
+                               for (int i = 1; i <= 100; i++) {
+                                       if (DateTime.Now >= limit) {
+                                               yield break;
+                                       }
+                                       yield return i;
+                               }
+                       } finally {
+                               Console.WriteLine("Stopping!");
+                       }
+               }
+
+               static IEnumerable<string> ReadLines (string filename)
+               {
+                       using (TextReader reader = File.OpenText(filename))
+                       {
+                               string line;
+                               while ((line = reader.ReadLine()) != null)
+                               {
+                                       yield return line;
+                               }
+                       }
+               }
        }
 
 

diff --git a/CSharpInDepth/Chapter6/Chapter6/bin/Debug/TheLayofLeithian.txt b/CSharpInDepth/Chapter6/Chapter6/bin/Debug/TheLayofLeithian.txt
new file mode 100644 (file)
index 0000000..3066d93
--- /dev/null
+++ b/CSharpInDepth/Chapter6/Chapter6/bin/Debug/TheLayofLeithian.txt
@@ -0,0 +1,5 @@
+Behold! the hope of Elvenland
+the fire of Fëanor, Light of Morn
+before the sun and moon were born,
+thus out of bondage came at last,
+from iron to mortal hand it passed.