.NET: [BREAKING] Support Checkpoint Serialization (#735)

* feat: Support Checkpoint Serialization

* Implements serialization roundtripping for checkpoints.
* Adds support for JSON serialization
* Adds FileSystem-based checkpoint persistence

* fix: Executor State does not deserialize correctly

The StateManager was not properly handling delay-deserialized values.

* Fix PortableValue handling in StateManager (this makes it delegate to PortableValue the uwnrapping)
* Fix UnitTest to actually test checkpoint serialization
* Additional review comment fixes

---------

Co-authored-by: Chris <66376200+crickman@users.noreply.github.com>

dotnet/samples/GettingStarted/Workflows/Checkpoint/CheckpointAndRehydrate/Program.cs

@@ -32,7 +32,7 @@ public static class Program
         var workflow = WorkflowHelper.GetWorkflow();
 
         // Create checkpoint manager
-        var checkpointManager = new CheckpointManager();
+        var checkpointManager = CheckpointManager.Default;
         var checkpoints = new List<CheckpointInfo>();
 
         // Execute the workflow and save checkpoints

dotnet/samples/GettingStarted/Workflows/Checkpoint/CheckpointAndResume/Program.cs

@@ -31,7 +31,7 @@ public static class Program
         var workflow = WorkflowHelper.GetWorkflow();
 
         // Create checkpoint manager
-        var checkpointManager = new CheckpointManager();
+        var checkpointManager = CheckpointManager.Default;
         var checkpoints = new List<CheckpointInfo>();
 
         // Execute the workflow and save checkpoints

dotnet/samples/GettingStarted/Workflows/Checkpoint/CheckpointWithHumanInTheLoop/Program.cs

@@ -34,7 +34,7 @@ public static class Program
         var workflow = WorkflowHelper.GetWorkflow();
 
         // Create checkpoint manager
-        var checkpointManager = new CheckpointManager();
+        var checkpointManager = CheckpointManager.Default;
         var checkpoints = new List<CheckpointInfo>();
 
         // Execute the workflow and save checkpoints
@@ -102,9 +102,9 @@ public static class Program
 
     private static ExternalResponse HandleExternalRequest(ExternalRequest request)
     {
-        if (request.Port.Request == typeof(SignalWithNumber))
+        var signal = request.DataAs<SignalWithNumber>();
+        if (signal is not null)
         {
-            var signal = (SignalWithNumber)request.Data;
             switch (signal.Signal)
             {
                 case NumberSignal.Init:
@@ -119,7 +119,7 @@ public static class Program
             }
         }
 
-        throw new NotSupportedException($"Request {request.Port.Request} is not supported");
+        throw new NotSupportedException($"Request {request.PortInfo.RequestType} is not supported");
     }
 
     private static int ReadIntegerFromConsole(string prompt)

dotnet/samples/GettingStarted/Workflows/ConditionalEdges/03_MultiSelection/Program.cs

@@ -75,10 +75,10 @@ public static class Program
         // After the email assistant writes a response, it will be sent to the send email executor
         .AddEdge(emailAssistantExecutor, sendEmailExecutor)
         // Save the analysis result to the database if summary is not needed
-        .AddEdge(
+        .AddEdge<AnalysisResult>(
             emailAnalysisExecutor,
             databaseAccessExecutor,
-            condition: analysisResult => analysisResult is AnalysisResult result && result.EmailLength <= LongEmailThreshold)
+            condition: analysisResult => analysisResult is not null && analysisResult.EmailLength <= LongEmailThreshold)
         // Save the analysis result to the database with summary
         .AddEdge(emailSummaryExecutor, databaseAccessExecutor);
         var workflow = builder.Build<ChatMessage>();
@@ -107,21 +107,21 @@ public static class Program
     /// Creates a partitioner for routing messages based on the analysis result.
     /// </summary>
     /// <returns>A function that takes an analysis result and returns the target partitions.</returns>
-    private static Func<object?, int, IEnumerable<int>> GetPartitioner()
+    private static Func<AnalysisResult?, int, IEnumerable<int>> GetPartitioner()
     {
         return (analysisResult, targetCount) =>
         {
-            if (analysisResult is AnalysisResult result)
+            if (analysisResult is not null)
             {
-                if (result.spamDecision == SpamDecision.Spam)
+                if (analysisResult.spamDecision == SpamDecision.Spam)
                 {
                     return [0]; // Route to spam handler
                 }
-                else if (result.spamDecision == SpamDecision.NotSpam)
+                else if (analysisResult.spamDecision == SpamDecision.NotSpam)
                 {
                     List<int> targets = [1]; // Route to the email assistant
 
-                    if (result.EmailLength > LongEmailThreshold)
+                    if (analysisResult.EmailLength > LongEmailThreshold)
                     {
                         targets.Add(2); // Route to the email summarizer too
                     }

dotnet/samples/GettingStarted/Workflows/Declarative/Program.cs

@@ -53,7 +53,7 @@ internal sealed class Program
         // Run the workflow, just like any other workflow
         string input = this.GetWorkflowInput();
 
-        CheckpointManager checkpointManager = new();
+        CheckpointManager checkpointManager = CheckpointManager.Default;
         Checkpointed<StreamingRun> run = await InProcessExecution.StreamAsync(workflow, input, checkpointManager);
 
         bool isComplete = false;
@@ -151,7 +151,7 @@ internal sealed class Program
                     Debug.WriteLine($"ACTION EXIT #{actionComplete.ActionId} [{actionComplete.ActionType}]");
                     break;
 
-                case ExecutorFailureEvent executorFailure:
+                case ExecutorFailedEvent executorFailure:
                     Debug.WriteLine($"STEP ERROR #{executorFailure.ExecutorId}: {executorFailure.Data?.Message ?? "Unknown"}");
                     break;
 
@@ -256,7 +256,7 @@ internal sealed class Program
     }
     private static InputResponse HandleExternalRequest(ExternalRequest request)
     {
-        InputRequest? message = request.Data as InputRequest;
+        InputRequest? message = request.Data.As<InputRequest>();
         string? userInput = null;
         do
         {

dotnet/samples/GettingStarted/Workflows/HumanInTheLoop/HumanInTheLoopBasic/Program.cs

@@ -50,9 +50,9 @@ public static class Program
 
     private static ExternalResponse HandleExternalRequest(ExternalRequest request)
     {
-        if (request.Port.Request == typeof(NumberSignal))
+        if (request.DataIs<NumberSignal>())
         {
-            var signal = (NumberSignal)request.Data;
+            var signal = request.DataAs<NumberSignal>();
             switch (signal)
             {
                 case NumberSignal.Init:
@@ -67,7 +67,7 @@ public static class Program
             }
         }
 
-        throw new NotSupportedException($"Request {request.Port.Request} is not supported");
+        throw new NotSupportedException($"Request {request.PortInfo.RequestType} is not supported");
     }
 
     private static int ReadIntegerFromConsole(string prompt)