Manage custom state data with Azure Cosmos DB for .NET in the v3 C# SDK


In this article, you’ll implement Azure Cosmos DB to store and manage your bot’s state data. The default Connector State Service used by bots is not intended for the production environment. You should either use Azure Extensions available on GitHub or implement a custom state client using data storage platform of your choice. Here are some of the reasons to use custom state storage:

  • Higher state API throughput (more control over performance)
  • Lower-latency for geo-distribution
  • Control over where the data is stored
  • Access to the actual state data
  • Store more than 32kb of data


You'll need:

Create Azure account

If you don't have an Azure account, click here to sign up for a free account.

Set up the Azure Cosmos DB database

  1. After you’ve logged into the Azure portal, create a new Azure Cosmos DB database by clicking New.
  2. Click Databases.
  3. Find Azure Cosmos DB and click Create.
  4. Fill in the fields. For the API field, select SQL (DocumentDB). When done filling in all the fields, click the Create button at the bottom of the screen to deploy the new database.
  5. After the new database is deployed, navigate to your new database. Click Access keys to find keys and connection strings. Your bot will use this information to call the storage service to save state data.

Install NuGet packages

  1. Open an existing C# bot project, or create a new one using the Bot template in Visual Studio.
  2. Install the following NuGet packages:
    • Microsoft.Bot.Builder.Azure
    • Autofac.WebApi2

Add connection string

Add the following entries into the Web.config file:

<add key="DocumentDbUrl" value="Your DocumentDB URI"/>
<add key="DocumentDbKey" value="Your DocumentDB Key"/>

You'll replace the value with your URI and Primary Key found in your Azure Cosmos DB. Save the Web.config file.

Modify your bot code

To use Azure Cosmos DB storage, add the following lines of code to your bot's Global.asax.cs file inside the Application_Start() method.

using System;
using Autofac;
using System.Web.Http;
using System.Configuration;
using Microsoft.Bot.Connector;
using Microsoft.Bot.Builder.Azure;
using Microsoft.Bot.Builder.Dialogs;
using Microsoft.Bot.Builder.Dialogs.Internals;

namespace SampleApp
    public class WebApiApplication : System.Web.HttpApplication
        protected void Application_Start()
            var uri = new Uri(ConfigurationManager.AppSettings["DocumentDbUrl"]);
            var key = ConfigurationManager.AppSettings["DocumentDbKey"];
            var store = new DocumentDbBotDataStore(uri, key);

                        builder =>
                            builder.Register(c => store)

                            builder.Register(c => new CachingBotDataStore(store, CachingBotDataStoreConsistencyPolicy.ETagBasedConsistency))



Save the global.asax.cs file. Now you are ready to test the bot with the emulator.

Run your bot app

Run your bot in Visual Studio, the code you added will create the custom botdata table in Azure.

Connect your bot to the emulator

At this point, your bot is running locally. Next, start the emulator and then connect to your bot in the emulator:

  1. Type http://localhost:port-number/api/messages into the address bar, where port-number matches the port number shown in the browser where your application is running. You can leave Microsoft App ID and Microsoft App Password fields blank for now. You'll get this information later when you register your bot.
  2. Click Connect.
  3. Test your bot by typing a few messages in the emulator.

View state data on Azure Portal

To view the state data, sign into your Azure portal and navigate to your database. Click Data Explorer (preview) to verify that the state information from your bot is being saved.

Next steps

In this article, you used Cosmos DB for saving and managing your bot's data. Next, learn how to model conversation flow by using dialogs.

Additional resources

If you are unfamiliar with Inversion of Control containers and Dependency Injection pattern used in the code above, visit Autofac site for information.

You can also download a sample from GitHub to learn more about using Cosmos DB for managing state.