docs: add M365 Extensions guide for .NET

teams.md/src/components/include/in-depth-guides/m365-extensions/csharp.incl.md

@@ -0,0 +1,76 @@
+<!-- setup -->
+
+Install the Microsoft 365 Extensions package alongside the Microsoft Agents SDK:
+
+```bash
+dotnet add package Microsoft.Agents.Hosting.AspNetCore
+dotnet add package Microsoft.Agents.Authentication.Msal
+dotnet add package Microsoft.Teams.M365Extensions
+```
+
+Add an Agents SDK host to your existing Teams SDK application, then register your Teams SDK bot with `AddTeamsSdk`:
+
+```csharp
+using Microsoft.Agents.Storage;
+using Microsoft.Teams.M365Extensions;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Your existing Microsoft Agents SDK agent
+builder.AddAgent<MyAgent>();
+builder.Services.AddSingleton<IStorage, MemoryStorage>();
+builder.Services.AddAgentAspNetAuthentication(builder.Configuration);
+
+// Embed your Teams SDK bot as middleware in the Agents SDK pipeline
+builder.Services.AddTeamsSdk<MyTeamsBot>();
+
+var app = builder.Build();
+
+app.UseAuthentication();
+app.UseAuthorization();
+app.MapAgentApplicationEndpoints(requireAuth: !app.Environment.IsDevelopment());
+
+app.Run();
+```
+
+<!-- channel-routing -->
+
+```csharp
+using Microsoft.Agents.Builder;
+using Microsoft.Agents.Builder.State;
+using Microsoft.Teams.M365Extensions;
+
+private async Task ChannelAsync(ITurnContext context, ITurnState state, CancellationToken ct)
+{
+    string via = TeamsSdkMiddleware.IsTeamsChannel(context.Activity)
+        ? "Teams turn with no matching teams.net route → fell through"
+        : "non-Teams channel → passed straight through";
+    await context.SendActivityAsync($"[Agent SDK] channelId={context.Activity.ChannelId} ({via})", cancellationToken: ct);
+}
+```
+
+<!-- agents-sdk-reaction -->
+
+```csharp
+using Microsoft.Agents.Builder;
+using Microsoft.Agents.Builder.State;
+using Microsoft.Teams.Apps.Schema;
+using Microsoft.Teams.M365Extensions;
+
+private async Task AgentsSdkReactAsync(ITurnContext context, ITurnState state, CancellationToken ct)
+{
+    if (!TeamsSdkMiddleware.IsTeamsChannel(context.Activity))
+    {
+        await context.SendActivityAsync("Message reactions are only available in Teams.", cancellationToken: ct);
+        return;
+    }
+
+    var response = await context.SendActivityAsync("Adding then removing a reaction.", cancellationToken: ct);
+    var api = _teamsBot.Api.ForServiceUrl(new Uri(context.Activity.ServiceUrl));
+    string conversationId = context.Activity.Conversation.Id;
+
+    await api.Conversations.AddReactionAsync(conversationId, response!.Id, ReactionTypes.Like, cancellationToken: ct);
+    await Task.Delay(2000, ct);
+    await api.Conversations.DeleteReactionAsync(conversationId, response.Id, ReactionTypes.Like, cancellationToken: ct);
+}
+```

teams.md/src/pages/templates/in-depth-guides/m365-extensions.mdx

@@ -3,14 +3,14 @@ sidebar_position: 8
 title: Microsoft 365 Extensions
 sidebar_label: Microsoft 365 Extensions
 summary: Bridge Teams SDK and Agents SDK for multichannel.
-languages: ['python', 'typescript']
+languages: ['python', 'typescript', 'csharp']
 ---
 
 # Microsoft 365 Extensions
 
 Microsoft 365 Extensions let you extend an existing Teams SDK application to channels such as Direct Line and Email without rewriting any Teams-specific capabilities.
 
-Register your existing Teams SDK handlers on the `App` returned by `useTeamsSdk` (TypeScript) or `use_teams_sdk` (Python).
+Register your existing Teams SDK handlers on the `App` returned by `useTeamsSdk` (TypeScript), `use_teams_sdk` (Python), or `AddTeamsSdk` (C#).
 Microsoft 365 Extensions work with your existing Teams SDK configuration and handlers.
 This app is a bridge where Microsoft Agents SDK `AgentApplication` acts the multichannel host.
 
@@ -55,12 +55,12 @@ When an Agents SDK handler receives a Teams activity, it can use the Teams SDK A
 <LanguageInclude section="agents-sdk-reaction" />
 
 
-For a full example, the <LanguageInclude content={{"typescript": "[TypeScript Microsoft 365 Extensions sample](https://github.com/microsoft/teams.ts/tree/main/examples/m365extensions)", "python": "[Python Microsoft 365 Extensions sample](https://github.com/microsoft/teams.py/tree/main/examples/m365extensions)"}} /> demonstrates a single application running across Teams, Web Chat, and Email.
+For a full example, the <LanguageInclude content={{"typescript": "[TypeScript Microsoft 365 Extensions sample](https://github.com/microsoft/teams.ts/tree/main/examples/m365extensions)", "python": "[Python Microsoft 365 Extensions sample](https://github.com/microsoft/teams.py/tree/main/examples/m365extensions)", "csharp": "[.NET Microsoft 365 Extensions sample](https://github.com/microsoft/teams.net/tree/main/samples/M365ExtensionsBot)"}} /> demonstrates a single application running across Teams, Web Chat, and Email.
 
 ## How It Works
 
 Microsoft 365 Extensions adds a lightweight middleware bridge to your existing Teams SDK application. Aside from app initialization, your Teams-specific code stays the same.
 
-1. **Add the bridge.** Call `useTeamsSdk` (Typescript) or `use_teams_sdk` (Python) to connect your app to Agents SDK.
+1. **Add the bridge.** Call `useTeamsSdk` (TypeScript), `use_teams_sdk` (Python), or `AddTeamsSdk` (C#) to connect your app to Agents SDK.
 2. **Keep your Teams logic.** Existing handlers and API client calls continue handling Teams activities.
-3. **Add more channels.** Direct Line, Email, and unmatched Teams activities flow to the Agents SDK.
+3. **Add more channels.** Direct Line, Email, and unmatched Teams activities flow to the Agents SDK.

teams.md/static/missing-pages.json

@@ -14,9 +14,6 @@
     "typescript",
     "python"
   ],
-  "in-depth-guides/m365-extensions": [
-    "csharp"
-  ],
   "in-depth-guides/observability/logging": [
     "csharp"
   ],