.NET: [BREAKING] Refactor providers to move common functionality to base

[westey-m]

Motivation and Context

All providers have common filtering, state bag access and source stamping, so moving common functionality to base classes.

Description

• Move common functionality to base classes

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR refactors provider classes to consolidate common functionality into base classes, introducing a template method pattern and generic state management. The refactoring moves filtering, state management, and source stamping logic from individual provider implementations into ChatHistoryProvider, AIContextProvider, and their new generic variants ChatHistoryProvider<TState> and AIContextProvider<TState>.

Changes:

• Introduced generic base classes ChatHistoryProvider<TState> and AIContextProvider<TState> that consolidate state management (GetOrInitializeState, SaveState) with StateKey and JsonSerializerOptions handling
• Refactored base provider classes to use template method pattern: sealed InvokingCoreAsync/InvokedCoreAsync methods now call overridable ProvideChatHistoryAsync/StoreChatHistoryAsync (for ChatHistoryProvider) and ProvideAIContextAsync/StoreAIContextAsync (for AIContextProvider)
• Moved message filtering logic to base class constructors with default implementations (ChatHistory excludes ChatHistory-sourced messages from storage; AIContext includes only External messages)
• Updated all concrete provider implementations and tests to work with the new base class structure
• Renamed RetrievalOutputMessageFilter to ProvideOutputMessageFilter for consistency

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
dotnet/src/Microsoft.Agents.AI.Abstractions/ChatHistoryProvider{TState}.cs	New generic base class providing typed state management for ChatHistoryProvider implementations
dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider{TState}.cs	New generic base class providing typed state management for AIContextProvider implementations
dotnet/src/Microsoft.Agents.AI.Abstractions/ChatHistoryProvider.cs	Refactored to template method pattern with ProvideChatHistoryAsync/StoreChatHistoryAsync, added constructor for filters
dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs	Refactored to template method pattern with ProvideAIContextAsync/StoreAIContextAsync, added constructor for filters
dotnet/src/Microsoft.Agents.AI.Abstractions/InMemoryChatHistoryProvider.cs	Updated to extend ChatHistoryProvider and pass filters to base constructor
dotnet/src/Microsoft.Agents.AI.Abstractions/InMemoryChatHistoryProviderOptions.cs	Renamed RetrievalOutputMessageFilter to ProvideOutputMessageFilter
dotnet/src/Microsoft.Agents.AI.CosmosNoSql/CosmosChatHistoryProvider.cs	Updated to extend ChatHistoryProvider, removed properties in favor of constructor parameters (breaking change)
dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowChatHistoryProvider.cs	Updated to extend ChatHistoryProvider, removed duplicate state management code
dotnet/src/Microsoft.Agents.AI/Memory/ChatHistoryMemoryProvider.cs	Updated to extend AIContextProvider, removed duplicate state management and filter code
dotnet/src/Microsoft.Agents.AI/TextSearchProvider.cs	Updated to extend AIContextProvider, removed duplicate state and filter code, made State class public
dotnet/src/Microsoft.Agents.AI.Mem0/Mem0Provider.cs	Updated to extend AIContextProvider, moved state validation to wrapper function
dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/ChatHistoryProviderTests.cs	Added comprehensive tests for new base class functionality
dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/ChatHistoryProviderTStateTests.cs	New test file for ChatHistoryProvider functionality
dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/AIContextProviderTests.cs	Added comprehensive tests for new base class functionality
dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/AIContextProviderTStateTests.cs	New test file for AIContextProvider functionality
dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/*.cs	Updated Mock instantiations to pass null parameters to new base class constructors
dotnet/tests/Microsoft.Agents.AI.CosmosNoSql.UnitTests/CosmosChatHistoryProviderTests.cs	Updated to use constructor parameters instead of property setters, updated comment
dotnet/samples/GettingStarted/Agents/Agent_Step07_3rdPartyChatHistoryStorage/Program.cs	Updated VectorChatHistoryProvider to extend ChatHistoryProvider
dotnet/samples/GettingStarted/AgentWithMemory/AgentWithMemory_Step03_CustomMemory/Program.cs	Updated UserInfoMemory to extend AIContextProvider

[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated 3 comments.