title	description	author	ms.date	ms.topic	ms.author	zone_pivot_groups
Connect Azure Functions to Azure Cosmos DB using Visual Studio Code	Learn how to connect Azure Functions to an Azure Cosmos DB account by adding an output binding to your Visual Studio Code project.	ThomasWeiss	08/17/2021	quickstart	thweiss	programming-languages-set-functions-temp

Connect Azure Functions to Azure Cosmos DB using Visual Studio Code

[!INCLUDE functions-add-storage-binding-intro]

This article shows you how to use Visual Studio Code to connect Azure Cosmos DB to the function you created in the previous quickstart article. The output binding that you add to this function writes data from the HTTP request to a JSON document stored in an Azure Cosmos DB container.

::: zone pivot="programming-language-csharp" Before you begin, you must complete the quickstart: Create a C# function in Azure using Visual Studio Code. If you already cleaned up resources at the end of that article, go through the steps again to recreate the function app and related resources in Azure. ::: zone-end ::: zone pivot="programming-language-javascript"
Before you begin, you must complete the quickstart: Create a JavaScript function in Azure using Visual Studio Code. If you already cleaned up resources at the end of that article, go through the steps again to recreate the function app and related resources in Azure.
::: zone-end

Configure your environment

Before you get started, make sure to install the Azure Databases extension for Visual Studio Code.

Create your Azure Cosmos DB account

Important

Azure Cosmos DB serverless is now generally available. This consumption-based mode makes Azure Cosmos DB a strong option for serverless workloads. To use Azure Cosmos DB in serverless mode, choose Serverless as the Capacity mode when creating your account.

In Visual Studio Code, choose the Azure icon in the Activity bar.
In the Azure: Databases area, right-click (Ctrl+click on macOS) on the Azure subscription where you created your function app in the previous article, and select Create Server...

:::image type="content" source="./media/functions-add-output-binding-cosmos-db-vs-code/create-account.png" alt-text="Creating a new Azure Cosmos DB account from Visual Studio code" border="true":::

Provide the following information at the prompts:

Prompt	Selection
Select an Azure Database Server	Choose `Core (SQL)` to create a document database that you can query by using a SQL syntax. Learn more about the Azure Cosmos DB SQL API.
Account name	Enter a unique name to identify your Azure Cosmos DB account. The account name can use only lowercase letters, numbers, and hyphens (-), and must be between 3 and 31 characters long.
Select a capacity model	Select Serverless to create an account in serverless mode.
Select a resource group for new resources	Choose the resource group where you created your function app in the previous article.
Select a location for new resources	Select a geographic location to host your Azure Cosmos DB account. Use the location that's closest to you or your users to get the fastest access to your data.

After your new account is provisioned, a message is displayed in notification area.

Create an Azure Cosmos DB database and container

Right-click your account and select Create database....
Provide the following information at the prompts:

Prompt Selection

Database name Type my-database.

Enter and ID for your collection Type my-container.

Enter the partition key for the collection Type /id as the partition key.
Select OK to create the container and database.

Update your function app settings

In the previous quickstart article, you created a function app in Azure. In this article, you update your app to write JSON documents to the Azure Cosmos DB container you've just created. To connect to your Azure Cosmos DB account, you must add its connection string to your app settings. You then download the new setting to your local.settings.json file so you can connect to your Azure Cosmos DB account when running locally.

In Visual Studio Code, right-click (Ctrl+click on macOS) on your new Azure Cosmos DB account, and select Copy Connection String.

:::image type="content" source="./media/functions-add-output-binding-cosmos-db-vs-code/copy-connection-string.png" alt-text="Copying the Azure Cosmos DB connection string" border="true":::
Press F1 to open the command palette, then search for and run the command Azure Functions: Add New Setting....

Choose the function app you created in the previous article. Provide the following information at the prompts:

Prompt	Selection
Enter new app setting name	Type `CosmosDbConnectionString`.
Enter value for "CosmosDbConnectionString"	Paste the connection string of your Azure Cosmos DB account you just copied.

This creates a application setting named connection CosmosDbConnectionString in your function app in Azure. Now, you can download this setting to your local.settings.json file.

Press F1 again to open the command palette, then search for and run the command Azure Functions: Download Remote Settings....
Choose the function app you created in the previous article. Select Yes to all to overwrite the existing local settings.

This downloads all of the setting from Azure to your local project, including the new connection string setting. Most of the downloaded settings aren't used when running locally.

Register binding extensions

Because you're using an Azure Cosmos DB output binding, you must have the corresponding bindings extension installed before you run the project.

::: zone pivot="programming-language-csharp"

With the exception of HTTP and timer triggers, bindings are implemented as extension packages. Run the following dotnet add package command in the Terminal window to add the Azure Cosmos DB extension package to your project.

In-process

dotnet add package Microsoft.Azure.WebJobs.Extensions.CosmosDB

Isolated process

dotnet add package Microsoft.Azure.Functions.Worker.Extensions.CosmosDB

Now, you can add the storage output binding to your project.
::: zone-end

::: zone pivot="programming-language-javascript"

Your project has been configured to use extension bundles, which automatically installs a predefined set of extension packages.

Extension bundles usage is enabled in the host.json file at the root of the project, which appears as follows:

:::code language="json" source="~/functions-quickstart-java/functions-add-output-binding-storage-queue/host.json":::

::: zone-end

Now, you can add the Azure Cosmos DB output binding to your project.

Add an output binding

In Functions, each type of binding requires a direction, type, and a unique name to be defined in the function.json file. The way you define these attributes depends on the language of your function app.

::: zone pivot="programming-language-csharp"

In a C# class library project, the bindings are defined as binding attributes on the function method. The function.json file required by Functions is then auto-generated based on these attributes.

In-process

Open the HttpExample.cs project file and add the following parameter to the Run method definition:

:::code language="csharp" source="~/functions-docs-csharp/functions-add-output-binding-cosmos-db/HttpExample.cs" range="18-20":::

The documentsOut parameter is an IAsyncCollector<T> type, which represents a collection of JSON documents that are written to your Azure Cosmos DB container when the function completes. Specific attributes indicate the names of the container and its parent database. The connection string for your Azure Cosmos DB account is set by the ConnectionStringSettingAttribute.

Isolated process

Open the HttpExample.cs project file and add the following classes:

:::code language="csharp" source="~/functions-docs-csharp/functions-add-output-binding-cosmos-db-isolated/HttpExample.cs" range="36-46":::

The MyDocument class defines an object that gets written to the database. The connection string for the Storage account is set by the Connection property. In this case, you could omit Connection because you are already using the default storage account.

The MultiResponse class allows you to both write to the specified collection in the Azure Cosmos DB and return an HTTP success message. Because you need to return a MultiResponse object, you need to also update the method signature.

Specific attributes specify the name of the container and the name of its parent database. The connection string for your Azure Cosmos DB account is set by the CosmosDbConnectionString.

::: zone-end

::: zone pivot="programming-language-javascript"

Binding attributes are defined directly in the function.json file. Depending on the binding type, additional properties may be required. The Azure Cosmos DB output configuration describes the fields required for an Azure Cosmos DB output binding. The extension makes it easy to add bindings to the function.json file.

To create a binding, right-click (Ctrl+click on macOS) the function.json file in your HttpTrigger folder and choose Add binding.... Follow the prompts to define the following binding properties for the new binding:

Prompt	Value	Description
Select binding direction	`out`	The binding is an output binding.
Select binding with direction "out"	`Azure Cosmos DB`	The binding is an Azure Cosmos DB binding.
The name used to identify this binding in your code	`outputDocument`	Name that identifies the binding parameter referenced in your code.
The Cosmos DB database where data will be written	`my-database`	The name of the Azure Cosmos DB database containing the target container.
Database collection where data will be written	`my-container`	The name of the Azure Cosmos DB container where the JSON documents will be written.
If true, creates the Cosmos DB database and collection	`false`	The target database and container already exist.
Select setting from "local.setting.json"	`CosmosDbConnectionString`	The name of an application setting that contains the connection string for the Azure Cosmos DB account.
Partition key (optional)	leave blank	Only required when the output binding creates the container.
Collection throughput (optional)	leave blank	Only required when the output binding creates the container.

A binding is added to the bindings array in your function.json, which should look like the following:

{
    "type": "cosmosDB",
    "direction": "out",
    "name": "outputDocument",
    "databaseName": "my-database",
    "collectionName": "my-container",
    "createIfNotExists": "false",
    "connectionStringSetting": "CosmosDbConnectionString"
}

::: zone-end

Add code that uses the output binding

::: zone pivot="programming-language-csharp"

In-process

Add code that uses the documentsOut output binding object to create a JSON document. Add this code before the method returns.

if (!string.IsNullOrEmpty(name))
{
    // Add a JSON document to the output container.
    await documentsOut.AddAsync(new
    {
        // create a random ID
        id = System.Guid.NewGuid().ToString(),
        name = name
    });
}

At this point, your function should look as follows:

[FunctionName("HttpExample")]
public static async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req,
    [CosmosDB(
        databaseName: "my-database",
        collectionName: "my-container",
        ConnectionStringSetting = "CosmosDbConnectionString")]IAsyncCollector<dynamic> documentsOut,
    ILogger log)
{
    log.LogInformation("C# HTTP trigger function processed a request.");

    string name = req.Query["name"];

    string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
    dynamic data = JsonConvert.DeserializeObject(requestBody);
    name = name ?? data?.name;

    if (!string.IsNullOrEmpty(name))
    {
        // Add a JSON document to the output container.
        await documentsOut.AddAsync(new
        {
            // create a random ID
            id = System.Guid.NewGuid().ToString(),
            name = name
        });
    }

    string responseMessage = string.IsNullOrEmpty(name)
        ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response."
        : $"Hello, {name}. This HTTP triggered function executed successfully.";

    return new OkObjectResult(responseMessage);
}

Isolated process

Replace the existing Run method with the following code:

:::code language="csharp" source="~/functions-docs-csharp/functions-add-output-binding-cosmos-db-isolated/HttpExample.cs" range="11-34":::

::: zone-end

::: zone pivot="programming-language-javascript"

Add code that uses the outputDocument output binding object on context.bindings to create a JSON document. Add this code before the context.res statement.

if (name) {
    context.bindings.outputDocument = JSON.stringify({
        // create a random ID
        id: new Date().toISOString() + Math.random().toString().substr(2,8),
        name: name
    });
}

At this point, your function should look as follows:

module.exports = async function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.');

    const name = (req.query.name || (req.body && req.body.name));
    const responseMessage = name
        ? "Hello, " + name + ". This HTTP triggered function executed successfully."
        : "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.";

    if (name) {
        context.bindings.outputDocument = JSON.stringify({
            // create a random ID
            id: new Date().toISOString() + Math.random().toString().substr(2,8),
            name: name
        });
    }

    context.res = {
        // status: 200, /* Defaults to 200 */
        body: responseMessage
    };
}

This code now returns a MultiResponse object that contains both a document and an HTTP response.

::: zone-end

::: zone pivot="programming-language-csharp" [!INCLUDE functions-run-function-test-local-vs-code-csharp] ::: zone-end

::: zone pivot="programming-language-javascript"

Run the function locally

As in the previous article, press F5 to start the function app project and Core Tools.
With Core Tools running, go to the Azure: Functions area. Under Functions, expand Local Project > Functions. Right-click (Ctrl-click on Mac) the HttpExample function and choose Execute Function Now....

:::image type="content" source="../../includes/media/functions-run-function-test-local-vs-code/execute-function-now.png" alt-text="Execute function now from Visual Studio Code":::
In Enter request body you see the request message body value of { "name": "Azure" }. Press Enter to send this request message to your function.
After a response is returned, press Ctrl + C to stop Core Tools. ::: zone-end

Verify that a JSON document has been created

On the Azure portal, go back to your Azure Cosmos DB account and select Data Explorer.
Expand your database and container, and select Items to list the documents created in your container.
Verify that a new JSON document has been created by the output binding.

:::image type="content" source="./media/functions-add-output-binding-cosmos-db-vs-code/verify-output.png" alt-text="Verifying that a new document has been created in the Azure Cosmos DB container" border="true":::

Redeploy and verify the updated app

In Visual Studio Code, press F1 to open the command palette. In the command palette, search for and select Azure Functions: Deploy to function app....
Choose the function app that you created in the first article. Because you're redeploying your project to the same app, select Deploy to dismiss the warning about overwriting files.
After deployment completes, you can again use the Execute Function Now... feature to trigger the function in Azure.
Again check the documents created in your Azure Cosmos DB container to verify that the output binding again generates a new JSON document.

Clean up resources

In Azure, resources refer to function apps, functions, storage accounts, and so forth. They're grouped into resource groups, and you can delete everything in a group by deleting the group.

You created resources to complete these quickstarts. You may be billed for these resources, depending on your account status and service pricing. If you don't need the resources anymore, here's how to delete them:

[!INCLUDE functions-cleanup-resources-vs-code-inner.md]

Next steps

You've updated your HTTP triggered function to write JSON documents to an Azure Cosmos DB container. Now you can learn more about developing Functions using Visual Studio Code:

Develop Azure Functions using Visual Studio Code
Azure Functions triggers and bindings. ::: zone pivot="programming-language-csharp"
Examples of complete Function projects in C#.
Azure Functions C# developer reference
::: zone-end ::: zone pivot="programming-language-javascript"
Examples of complete Function projects in JavaScript.
Azure Functions JavaScript developer guide
::: zone-end

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functions-add-output-binding-cosmos-db-vs-code.md

functions-add-output-binding-cosmos-db-vs-code.md

Connect Azure Functions to Azure Cosmos DB using Visual Studio Code

Configure your environment

Create your Azure Cosmos DB account

Create an Azure Cosmos DB database and container

Update your function app settings

Register binding extensions

In-process

Isolated process

Add an output binding

In-process

Isolated process

Add code that uses the output binding

In-process

Isolated process

Run the function locally

Verify that a JSON document has been created

Redeploy and verify the updated app

Clean up resources

Next steps

Prompt	Selection
Database name	Type `my-database`.
Enter and ID for your collection	Type `my-container`.
Enter the partition key for the collection	Type `/id` as the partition key.

Files

functions-add-output-binding-cosmos-db-vs-code.md

Latest commit

History

functions-add-output-binding-cosmos-db-vs-code.md

File metadata and controls

Connect Azure Functions to Azure Cosmos DB using Visual Studio Code

Configure your environment

Create your Azure Cosmos DB account

Create an Azure Cosmos DB database and container

Update your function app settings

Register binding extensions

In-process

Isolated process

Add an output binding

In-process

Isolated process

Add code that uses the output binding

In-process

Isolated process

Run the function locally

Verify that a JSON document has been created

Redeploy and verify the updated app

Clean up resources

Next steps