Fix cancellation by polling example (#31643) (#31695)

* Fix cs example by moving check out of loop (#31643)

* Fix vs example by moving check out of loop (#31643)

* Fix variable scope and comments (#31643)

* Add project files (#31643)

* Apply suggestions from code review

Co-authored-by: David Pine <david.pine@microsoft.com>

Co-authored-by: Bill Wagner <wiwagn@microsoft.com>
Co-authored-by: David Pine <david.pine@microsoft.com>

Author: 3 people

samples/snippets/csharp/VS_Snippets_Misc/cancellation/cs/cancellation.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+</Project>

samples/snippets/csharp/VS_Snippets_Misc/cancellation/cs/cancellationex11.cs

@@ -40,24 +40,24 @@ static void Main()
    //<snippet3>
    static void NestedLoops(Rectangle rect, CancellationToken token)
    {
-      for (int x = 0; x < rect.columns && !token.IsCancellationRequested; x++) {
-         for (int y = 0; y < rect.rows; y++) {
+      for (int col = 0; col < rect.columns && !token.IsCancellationRequested; col++) {
+         // Assume that we know that the inner loop is very fast.
+         // Therefore, polling once per column in the outer loop condition
+         // is sufficient.
+         for (int row = 0; row < rect.rows; row++) {
             // Simulating work.
-            Thread.SpinWait(5000);
-            Console.Write("{0},{1} ", x, y);
+            Thread.SpinWait(5_000);
+            Console.Write("{0},{1} ", col, row);
          }
+      }
 
-         // Assume that we know that the inner loop is very fast.
-         // Therefore, checking once per row is sufficient.
-         if (token.IsCancellationRequested) {
-            // Cleanup or undo here if necessary...
-            Console.WriteLine("\r\nCancelling after row {0}.", x);
-            Console.WriteLine("Press any key to exit.");
-            // then...
-            break;
-            // ...or, if using Task:
-            // token.ThrowIfCancellationRequested();
-         }
+      if (token.IsCancellationRequested) {
+         // Cleanup or undo here if necessary...
+         Console.WriteLine("\r\nCancelling before column {0}.", col);
+         Console.WriteLine("Press any key to exit.");
+
+         // If using Task:
+         // token.ThrowIfCancellationRequested();
       }
    }
    //</snippet3>

samples/snippets/visualbasic/VS_Snippets_Misc/cancellation/vb/cancellation.vbproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+</Project>

samples/snippets/visualbasic/VS_Snippets_Misc/cancellation/vb/cancellationex11.vb

@@ -41,25 +41,26 @@ Class CancelByPolling
 
     '<snippet3>
     Shared Sub NestedLoops(ByVal rect As Rectangle, ByVal token As CancellationToken)
-        For x As Integer = 0 To rect.columns
-            For y As Integer = 0 To rect.rows
+        Dim col As Integer
+        For col = 0 To rect.columns - 1
+            ' Assume that we know that the inner loop is very fast.
+            ' Therefore, polling once per column in the outer loop condition
+            ' is sufficient.
+            For col As Integer = 0 To rect.rows - 1
                 ' Simulating work.
                 Thread.SpinWait(5000)
-                Console.Write("0' end block,1' end block ", x, y)
+                Console.Write("0',1' ", x, y)
             Next
-
-            ' Assume that we know that the inner loop is very fast.
-            ' Therefore, checking once per row is sufficient.
-            If token.IsCancellationRequested = True Then
-                ' Cleanup or undo here if necessary...
-                Console.WriteLine(vbCrLf + "Cancelling after row 0' end block.", x)
-                Console.WriteLine("Press any key to exit.")
-                ' then...
-                Exit For
-                ' ...or, if using Task:
-                ' token.ThrowIfCancellationRequested()
-            End If
         Next
+
+        If token.IsCancellationRequested = True Then
+            ' Cleanup or undo here if necessary...
+            Console.WriteLine(vbCrLf + "Cancelling before column 0'.", col)
+            Console.WriteLine("Press any key to exit.")
+
+            ' If using Task:
+            ' token.ThrowIfCancellationRequested()
+        End If
     End Sub
     '</snippet3>
 End Class