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redis-vl-dotnet

MessageHistory

MessageHistory is an append-only, session-scoped chat log stored in Redis hashes. It gives you recency-based retrieval without requiring vectorization.

Schema and ordering model

Each message history index stores:

  • sessionId

  • role

  • content

  • optional metadata JSON

  • timestamp

  • sequence

Messages are keyed by a hashed session id plus an incrementing sequence number. Retrieval is ordered by descending sequence, which gives you a stable most-recent-first history for one session.

Core operations

API Behavior

AppendAsync(sessionId, role, content, metadata, timestamp)

Appends one message and returns the Redis document key.

GetRecentAsync(sessionId, limit, role)

Returns the newest messages for one session, optionally narrowed to one role such as assistant.

CreateAsync, ExistsAsync, DropAsync

Manage the backing HASH index.

limit must be greater than zero. sessionId, role, and content are trimmed before they are stored.

Recency behavior

GetRecentAsync always scopes the query to one session id. If you pass role, the search adds a second TAG filter so you can fetch only assistant replies, only user turns, or another application-specific role.

This API does not do semantic retrieval. Use SemanticMessageHistory when you need nearest-message lookup inside the same session.

Example

Use /examples/MessageHistoryExample for the runnable history workflow in this repo.

That sample uses SemanticMessageHistory, but it demonstrates the same recency retrieval pattern through GetRecentAsync and the same session-oriented append model. For the exact non-vector API contract, use tests/RedisVL.Tests/Workflows/MessageHistoryTests.cs and tests/RedisVL.Tests/Workflows/MessageHistoryIntegrationTests.cs.

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