ChannelAdapterAttribute Class

Definition

Namespace:

Microsoft.Agents.Builder.Adapters

Assembly:

Microsoft.Agents.Builder.dll

Package:

Microsoft.Agents.Builder v1.8.77

Declares that an IChannelAdapter implementation handles inbound requests for a specific channelId. Annotated adapters are auto-registered in the IChannelAdapterRegistry so that shared-endpoint (Tier 2) dispatch and SDK features (proactive messaging, diagnostics) can resolve the correct adapter by channelId.

[System.AttributeUsage(System.AttributeTargets.Class, AllowMultiple=true, Inherited=false)]
public sealed class ChannelAdapterAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Class, AllowMultiple=true, Inherited=false)>]
type ChannelAdapterAttribute = class
    inherit Attribute

Public NotInheritable Class ChannelAdapterAttribute
Inherits Attribute

Inheritance

Attribute

ChannelAdapterAttribute

Attributes

AttributeUsageAttribute

Remarks

This attribute operates like Microsoft.Agents.Core.Serialization.ActivityTypeAttribute: a source generator (ChannelAdapterInitSourceGenerator) emits an assembly-level ChannelAdapterInitAssemblyAttribute for every annotated adapter, and those assembly attributes are read off the loaded assemblies at runtime — so no explicit DI registration call (such as AddChannelAdapter) is required. Simply reference the assembly that declares the annotated adapter.

The annotated type must implement IChannelAdapter (so it can be resolved through IChannelAdapterRegistry) and should be public so consuming applications can preload its assembly; to also serve shared-endpoint HTTP dispatch it must implement the host's HTTP adapter contract (IAgentHttpAdapter in Microsoft.Agents.Hosting.AspNetCore). Both hold for adapters deriving from CloudAdapter or ChannelAdapter. It does not need to derive from CloudAdapter — the default Activity Protocol adapter (CloudAdapter) remains the registry default and is not annotated.

// Handles only Teams traffic routed through the shared /api/messages endpoint:
[ChannelAdapter("msteams")]
public class TeamsChannelAdapter : CloudAdapter { }

// A dedicated-protocol adapter that also participates in the registry:
[ChannelAdapter("a2a")]
public class A2AAdapter : ChannelAdapter, IAgentHttpAdapter { }

Constructors

Name	Description
ChannelAdapterAttribute(String)	Initializes a new instance of the ChannelAdapterAttribute class.

Properties

Name	Description
ChannelId	The channelId this adapter handles (e.g., "msteams", "a2a").