.NET: Chathistory memory provider add (#1867)

* Add ChatHistoryMemoryProvider with unit tests

* Set new project to not packable.

* Fix bugs

* Add serialization support.

* Update dotnet/src/Microsoft.Agents.AI.VectorDataMemory/ChatHistoryMemoryProvider.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Remove unnecessary line

* Convert ChatHistoryMemoryProvider to use Dynamic collections.

* Sealing options and scope classes.

* Add sample, add scope to logs and improve scope validation

* Move ChatHistoryMemoryProvider to MAAI project.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

dotnet/samples/GettingStarted/Agents/Agent_Step18_TextSearchRag/Program.cs

@@ -4,6 +4,8 @@
 // capabilities to an AI agent. The provider runs a search against an external knowledge base
 // before each model invocation and injects the results into the model context.
 
+// Also see the AgentWithRAG folder for more advanced RAG scenarios.
+
 using Azure.AI.OpenAI;
 using Azure.Identity;
 using Microsoft.Agents.AI;

dotnet/samples/GettingStarted/Agents/Agent_Step21_ChatHistoryMemoryProvider/Agent_Step21_ChatHistoryMemoryProvider.csproj

@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.AI.OpenAI" />
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Microsoft.Extensions.AI.OpenAI" />
+    <PackageReference Include="Microsoft.SemanticKernel.Connectors.InMemory" />
+    <PackageReference Include="System.Linq.Async" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.OpenAI\Microsoft.Agents.AI.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/GettingStarted/Agents/Agent_Step21_ChatHistoryMemoryProvider/Program.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample shows how to create and use a simple AI agent that stores chat messages in a vector store using the ChatHistoryMemoryProvider.
+// It can then use the chat history from prior conversations to inform responses in new conversations.
+
+using Azure.AI.OpenAI;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+using Microsoft.Extensions.VectorData;
+using Microsoft.SemanticKernel.Connectors.InMemory;
+using OpenAI;
+
+var endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? throw new InvalidOperationException("AZURE_OPENAI_ENDPOINT is not set.");
+var deploymentName = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT_NAME") ?? "gpt-4o-mini";
+var embeddingDeploymentName = Environment.GetEnvironmentVariable("AZURE_OPENAI_EMBEDDING_DEPLOYMENT_NAME") ?? "text-embedding-3-large";
+
+// Create a vector store to store the chat messages in.
+// For demonstration purposes, we are using an in-memory vector store.
+// Replace this with a vector store implementation of your choice that can persist the chat history long term.
+VectorStore vectorStore = new InMemoryVectorStore(new InMemoryVectorStoreOptions()
+{
+    EmbeddingGenerator = new AzureOpenAIClient(new Uri(endpoint), new AzureCliCredential())
+        .GetEmbeddingClient(embeddingDeploymentName)
+        .AsIEmbeddingGenerator()
+});
+
+// Create the agent and add the ChatHistoryMemoryProvider to store chat messages in the vector store.
+AIAgent agent = new AzureOpenAIClient(
+    new Uri(endpoint),
+    new AzureCliCredential())
+    .GetChatClient(deploymentName)
+    .CreateAIAgent(new ChatClientAgentOptions
+    {
+        Instructions = "You are good at telling jokes.",
+        Name = "Joker",
+        AIContextProviderFactory = (ctx) => new ChatHistoryMemoryProvider(
+            vectorStore,
+            collectionName: "chathistory",
+            vectorDimensions: 3072,
+            // Configure the scope values under which chat messages will be stored.
+            // In this case, we are using a fixed user ID and a unique thread ID for each new thread.
+            storageScope: new() { UserId = "UID1", ThreadId = new Guid().ToString() },
+            // Configure the scope which would be used to search for relevant prior messages.
+            // In this case, we are searching for any messages for the user across all threads.
+            searchScope: new() { UserId = "UID1" })
+    });
+
+// Start a new thread for the agent conversation.
+AgentThread thread = agent.GetNewThread();
+
+// Run the agent with the thread that stores conversation history in the vector store.
+Console.WriteLine(await agent.RunAsync("I like jokes about Pirates. Tell me a joke about a pirate.", thread));
+
+// Start a second thread. Since we configured the search scope to be across all threads for the user,
+// the agent should remember that the user likes pirate jokes.
+AgentThread thread2 = agent.GetNewThread();
+
+// Run the agent with the second thread.
+Console.WriteLine(await agent.RunAsync("Tell me a joke that I might like.", thread2));