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.NET: Fix filter combine logic for ChatHistoryMemoryProvider (#4501)

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* Fix filter combine logic for ChatHistoryMemoryProvider

* Replace var with explicit types in filter building code and test

Address PR review nit: use explicit types instead of var for better
readability in the filter-building logic and the new combined filter
compilation test.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix style issues

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
westey
2026-03-06 11:59:50 +00:00
committed by GitHub
Unverified
parent d8d6ac1c59
commit f7e4143c61
2 changed files with 108 additions and 14 deletions
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dotnet/src/Microsoft.Agents.AI/Memory/ChatHistoryMemoryProvider.cs
+37 -14
View File
@@ -350,36 +350,38 @@ public sealed class ChatHistoryMemoryProvider : MessageAIContextProvider, IDispo
string? userId = searchScope.UserId;
string? sessionId = searchScope.SessionId;
Expression<Func<Dictionary<string, object?>, bool>>? filter = null;
// Build a combined filter using a single shared parameter to avoid expression tree
// scoping issues when multiple filters are combined with AndAlso.
ParameterExpression parameter = Expression.Parameter(typeof(Dictionary<string, object?>), "x");
Expression? filterBody = null;
if (applicationId != null)
{
filter = x => (string?)x[ApplicationIdField] == applicationId;
filterBody = RebindFilterBody(x => (string?)x[ApplicationIdField] == applicationId, parameter);
}
if (agentId != null)
{
Expression<Func<Dictionary<string, object?>, bool>> agentIdFilter = x => (string?)x[AgentIdField] == agentId;
filter = filter == null ? agentIdFilter : Expression.Lambda<Func<Dictionary<string, object?>, bool>>(
Expression.AndAlso(filter.Body, agentIdFilter.Body),
filter.Parameters);
Expression body = RebindFilterBody(x => (string?)x[AgentIdField] == agentId, parameter);
filterBody = filterBody == null ? body : Expression.AndAlso(filterBody, body);
}
if (userId != null)
{
Expression<Func<Dictionary<string, object?>, bool>> userIdFilter = x => (string?)x[UserIdField] == userId;
filter = filter == null ? userIdFilter : Expression.Lambda<Func<Dictionary<string, object?>, bool>>(
Expression.AndAlso(filter.Body, userIdFilter.Body),
filter.Parameters);
Expression body = RebindFilterBody(x => (string?)x[UserIdField] == userId, parameter);
filterBody = filterBody == null ? body : Expression.AndAlso(filterBody, body);
}
if (sessionId != null)
{
Expression<Func<Dictionary<string, object?>, bool>> sessionIdFilter = x => (string?)x[SessionIdField] == sessionId;
filter = filter == null ? sessionIdFilter : Expression.Lambda<Func<Dictionary<string, object?>, bool>>(
Expression.AndAlso(filter.Body, sessionIdFilter.Body),
filter.Parameters);
Expression body = RebindFilterBody(x => (string?)x[SessionIdField] == sessionId, parameter);
filterBody = filterBody == null ? body : Expression.AndAlso(filterBody, body);
}
Expression<Func<Dictionary<string, object?>, bool>>? filter = filterBody != null
? Expression.Lambda<Func<Dictionary<string, object?>, bool>>(filterBody, parameter)
: null;
// Use search to find relevant messages
var searchResults = collection.SearchAsync(
queryText,
@@ -467,6 +469,27 @@ public sealed class ChatHistoryMemoryProvider : MessageAIContextProvider, IDispo
private string? SanitizeLogData(string? data) => this._enableSensitiveTelemetryData ? data : "<redacted>";
/// <summary>
/// Rebinds a filter expression's body to use the specified shared parameter,
/// replacing the original lambda parameter so that multiple filters can be safely
/// combined with <see cref="Expression.AndAlso(Expression, Expression)"/>.
/// </summary>
private static Expression RebindFilterBody(
Expression<Func<Dictionary<string, object?>, bool>> filter,
ParameterExpression sharedParameter)
{
return new ParameterReplacer(filter.Parameters[0], sharedParameter).Visit(filter.Body);
}
/// <summary>
/// An <see cref="ExpressionVisitor"/> that replaces one <see cref="ParameterExpression"/> with another.
/// </summary>
private sealed class ParameterReplacer(ParameterExpression original, ParameterExpression replacement) : ExpressionVisitor
{
protected override Expression VisitParameter(ParameterExpression node)
=> node == original ? replacement : base.VisitParameter(node);
}
/// <summary>
/// Represents the state of a <see cref="ChatHistoryMemoryProvider"/> stored in the <see cref="AgentSession.StateBag"/>.
/// </summary>
dotnet/tests/Microsoft.Agents.AI.UnitTests/Memory/ChatHistoryMemoryProviderTests.cs
+71
View File
@@ -454,6 +454,77 @@ public class ChatHistoryMemoryProviderTests
Times.Once);
}
[Fact]
public async Task InvokedAsync_CombinedFilterCanBeCompiled_WhenMultipleScopeFiltersProvidedAsync()
{
// Arrange
// This test reproduces a bug where combining multiple scope filters
// (e.g. userId + sessionId) produces an expression tree with dangling
// ParameterExpression references that fails at compile time.
ChatHistoryMemoryProviderOptions providerOptions = new()
{
SearchTime = ChatHistoryMemoryProviderOptions.SearchBehavior.BeforeAIInvoke,
MaxResults = 2,
ContextPrompt = "Here is the relevant chat history:\n"
};
ChatHistoryMemoryProviderScope searchScope = new()
{
ApplicationId = "app1",
AgentId = "agent1",
SessionId = "session1",
UserId = "user1"
};
System.Linq.Expressions.Expression<Func<Dictionary<string, object?>, bool>>? capturedFilter = null;
this._vectorStoreCollectionMock
.Setup(c => c.SearchAsync(
It.IsAny<string>(),
It.IsAny<int>(),
It.IsAny<VectorSearchOptions<Dictionary<string, object?>>>(),
It.IsAny<CancellationToken>()))
.Callback((string query, int maxResults, VectorSearchOptions<Dictionary<string, object?>> options, CancellationToken ct) =>
capturedFilter = options.Filter)
.Returns(ToAsyncEnumerableAsync(new List<VectorSearchResult<Dictionary<string, object?>>>()));
ChatHistoryMemoryProvider provider = new(
this._vectorStoreMock.Object,
TestCollectionName,
1,
_ => new ChatHistoryMemoryProvider.State(searchScope, searchScope),
options: providerOptions);
ChatMessage requestMsg = new(ChatRole.User, "requesting relevant history");
AIContextProvider.InvokingContext invokingContext = new(s_mockAgent, new TestAgentSession(), new AIContext { Messages = new List<ChatMessage> { requestMsg } });
// Act
await provider.InvokingAsync(invokingContext, CancellationToken.None);
// Assert - The filter must be compilable and executable without expression tree scoping errors
Assert.NotNull(capturedFilter);
Func<Dictionary<string, object?>, bool> compiledFilter = capturedFilter!.Compile();
Dictionary<string, object?> matchingRecord = new()
{
["ApplicationId"] = "app1",
["AgentId"] = "agent1",
["SessionId"] = "session1",
["UserId"] = "user1"
};
Dictionary<string, object?> nonMatchingRecord = new()
{
["ApplicationId"] = "app1",
["AgentId"] = "agent1",
["SessionId"] = "other-session",
["UserId"] = "user1"
};
Assert.True(compiledFilter(matchingRecord));
Assert.False(compiledFilter(nonMatchingRecord));
}
[Theory]
[InlineData(false, false, 2)]
[InlineData(true, false, 2)]