.NET: [BREAKING] Update providers in such a way that they can participate in a pipeline (#3846)

* Make providers pipeline capable

* Fix unit tests

* Move source stamping to providers from base class

* Also update samples.

* Address PR comments

* Rename AsAgentRequestMessageSourcedMessage to WithAgentRequestMessageSource

dotnet/samples/GettingStarted/AgentWithMemory/AgentWithMemory_Step03_CustomMemory/Program.cs

@@ -125,10 +125,15 @@ namespace SampleApp
 
         protected override ValueTask<AIContext> InvokingCoreAsync(InvokingContext context, CancellationToken cancellationToken = default)
         {
+            var inputContext = context.AIContext;
             var userInfo = context.Session?.StateBag.GetValue<UserInfo>(nameof(UserInfoMemory))
                 ?? this._stateInitializer.Invoke(context.Session);
 
             StringBuilder instructions = new();
+            if (!string.IsNullOrEmpty(inputContext.Instructions))
+            {
+                instructions.AppendLine(inputContext.Instructions);
+            }
 
             // If we don't already know the user's name and age, add instructions to ask for them, otherwise just provide what we have to the context.
             instructions
@@ -143,7 +148,9 @@ namespace SampleApp
 
             return new ValueTask<AIContext>(new AIContext
             {
-                Instructions = instructions.ToString()
+                Instructions = instructions.ToString(),
+                Messages = inputContext.Messages,
+                Tools = inputContext.Tools
             });
         }
     }

dotnet/samples/GettingStarted/Agents/Agent_Step07_3rdPartyChatHistoryStorage/Program.cs

@@ -126,7 +126,9 @@ namespace SampleApp
 
             var messages = records.ConvertAll(x => JsonSerializer.Deserialize<ChatMessage>(x.SerializedMessage!)!);
             messages.Reverse();
-            return messages;
+            return messages
+                .Select(message => message.WithAgentRequestMessageSource(AgentRequestMessageSourceType.ChatHistory, this.GetType().FullName!))
+                .Concat(context.RequestMessages);
         }
 
         protected override async ValueTask InvokedCoreAsync(InvokedContext context, CancellationToken cancellationToken = default)

dotnet/samples/GettingStarted/Agents/Agent_Step20_AdditionalAIContext/Program.cs

@@ -87,6 +87,7 @@ namespace SampleApp
 
         protected override ValueTask<AIContext> InvokingCoreAsync(InvokingContext context, CancellationToken cancellationToken = default)
         {
+            var inputContext = context.AIContext;
             var todoItems = GetTodoItems(context.Session);
 
             StringBuilder outputMessageBuilder = new();
@@ -106,12 +107,19 @@ namespace SampleApp
 
             return new ValueTask<AIContext>(new AIContext
             {
-                Tools =
-                [
+                Instructions = inputContext.Instructions,
+                Tools = (inputContext.Tools ?? []).Concat(new AITool[]
+                {
                     AIFunctionFactory.Create((string item) => AddTodoItem(context.Session, item), "AddTodoItem", "Adds an item to the todo list."),
                     AIFunctionFactory.Create((int index) => RemoveTodoItem(context.Session, index), "RemoveTodoItem", "Removes an item from the todo list. Index is zero based.")
-                ],
-                Messages = [new MEAI.ChatMessage(ChatRole.User, outputMessageBuilder.ToString())]
+                }).ToList(),
+                Messages =
+                    (inputContext.Messages ?? [])
+                    .Concat(
+                    [
+                        new MEAI.ChatMessage(ChatRole.User, outputMessageBuilder.ToString()).WithAgentRequestMessageSource(AgentRequestMessageSourceType.AIContextProvider, this.GetType().FullName!)
+                    ])
+                    .ToList()
             });
         }
 
@@ -142,6 +150,7 @@ namespace SampleApp
     {
         protected override async ValueTask<AIContext> InvokingCoreAsync(InvokingContext context, CancellationToken cancellationToken = default)
         {
+            var inputContext = context.AIContext;
             var events = await loadNextThreeCalendarEvents();
 
             StringBuilder outputMessageBuilder = new();
@@ -153,10 +162,15 @@ namespace SampleApp
 
             return new()
             {
+                Instructions = inputContext.Instructions,
                 Messages =
-                [
-                    new MEAI.ChatMessage(ChatRole.User, outputMessageBuilder.ToString()),
-                ]
+                    (inputContext.Messages ?? [])
+                    .Concat(
+                    [
+                        new MEAI.ChatMessage(ChatRole.User, outputMessageBuilder.ToString()).WithAgentRequestMessageSource(AgentRequestMessageSourceType.AIContextProvider, this.GetType().FullName!)
+                    ])
+                    .ToList(),
+                Tools = inputContext.Tools
             };
         }
     }
@@ -177,16 +191,13 @@ namespace SampleApp
         protected override async ValueTask<AIContext> InvokingCoreAsync(InvokingContext context, CancellationToken cancellationToken = default)
         {
             // Invoke all the sub providers.
-            var tasks = this._providers.Select(provider => provider.InvokingAsync(context, cancellationToken).AsTask());
-            var results = await Task.WhenAll(tasks);
-
-            // Combine the results from each sub provider.
-            return new AIContext
+            var currentAIContext = context.AIContext;
+            foreach (var provider in this._providers)
             {
-                Tools = results.SelectMany(r => r.Tools ?? []).ToList(),
-                Messages = results.SelectMany(r => r.Messages ?? []).ToList(),
-                Instructions = string.Join("\n", results.Select(r => r.Instructions).Where(s => !string.IsNullOrEmpty(s)))
-            };
+                currentAIContext = await provider.InvokingAsync(new InvokingContext(context.Agent, context.Session, currentAIContext), cancellationToken);
+            }
+
+            return currentAIContext;
         }
     }
 }