In this article, you use command-line tools to create a C# function that responds to HTTP requests. After testing the code locally, you deploy it to the serverless environment of Azure Functions.

This article creates an HTTP triggered function that runs on .NET 8 in an isolated worker process. For information about .NET versions supported for C# functions, see Supported versions. There's also a Visual Studio Code-based version of this article.

Completing this quickstart incurs a small cost of a few USD cents or less in your Azure account.

Before you begin, you must have the following:

• .NET 8.0 SDK.

• One of the following tools for creating Azure resources:

  • Azure CLI version 2.4 or later.

  • The Azure Az PowerShell module version 5.9.0 or later.

You also need an Azure account with an active subscription. Create an account for free.

[!INCLUDE functions-install-core-tools]

In Azure Functions, a function project is a container for one or more individual functions that each responds to a specific trigger. All functions in a project share the same local and hosting configurations. In this section, you create a function project that contains a single function.

1. Run the func init command, as follows, to create a functions project in a folder named LocalFunctionProj with the specified runtime:

   func init LocalFunctionProj --worker-runtime dotnet-isolated --target-framework net8.0

2. Navigate into the project folder:

   cd LocalFunctionProj

   This folder contains various files for the project, including configurations files named local.settings.json and host.json. Because local.settings.json can contain secrets downloaded from Azure, the file is excluded from source control by default in the .gitignore file.

3. Add a function to your project by using the following command, where the --name argument is the unique name of your function (HttpExample) and the --template argument specifies the function's trigger (HTTP).

   func new --name HttpExample --template "HTTP trigger" --authlevel "anonymous"

   func new creates an HttpExample.cs code file.

If desired, you can skip to Run the function locally and examine the file contents later.

HttpExample.cs contains a Run method that receives request data in the req variable as an HttpRequest object. That parameter is decorated with the HttpTriggerAttribute, to define the trigger behavior.

using System.Net;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace Company.Function
{
    public class HttpExample
    {
        private readonly ILogger<HttpExample> _logger;

        public HttpExample(ILogger<HttpExample> logger)
        {
            _logger = logger;
        }

        [Function("HttpExample")]
        public IActionResult Run([HttpTrigger(AuthorizationLevel.AuthLevelValue, "get", "post")] HttpRequest req)
        {            
            _logger.LogInformation("C# HTTP trigger function processed a request.");

            return new OkObjectResult("Welcome to Azure Functions!");
        }
    }
}

The return object is an IActionResult object that contains the data that's handed back to the HTTP response.

To learn more, see Azure Functions HTTP triggers and bindings.

1. Run your function by starting the local Azure Functions runtime host from the LocalFunctionProj folder:

   func start
   

   Toward the end of the output, the following lines should appear:

    ...
   
    Now listening on: http://0.0.0.0:7071
    Application started. Press Ctrl+C to shut down.
   
    Http Functions:
   
            HttpExample: [GET,POST] http://localhost:7071/api/HttpExample
    ...
   
    

   [!NOTE] If HttpExample doesn't appear as shown above, you likely started the host from outside the root folder of the project. In that case, use Ctrl+C to stop the host, navigate to the project's root folder, and run the previous command again.

2. Copy the URL of your HttpExample function from this output to a browser and browse to the function URL and you should receive a Welcome to Azure Functions message.

3. When you're done, use Ctrl+C and choose y to stop the functions host.

[!INCLUDE functions-create-azure-resources-cli]

4. Create the function app in Azure:

   Azure CLI

   az functionapp create --resource-group AzureFunctionsQuickstart-rg --consumption-plan-location <REGION> --runtime dotnet-isolated --functions-version 4 --name <APP_NAME> --storage-account <STORAGE_NAME>
   

   The az functionapp create command creates the function app in Azure.

   Azure PowerShell

   New-AzFunctionApp -Name <APP_NAME> -ResourceGroupName AzureFunctionsQuickstart-rg -StorageAccount <STORAGE_NAME> -Runtime dotnet-isolated -FunctionsVersion 4 -Location '<REGION>'
   

   The New-AzFunctionApp cmdlet creates the function app in Azure.

   ---

   In the previous example, replace <STORAGE_NAME> with the name of the account you used in the previous step, and replace <APP_NAME> with a globally unique name appropriate to you. The <APP_NAME> is also the default DNS domain for the function app.

   This command creates a function app running in your specified language runtime under the Azure Functions Consumption Plan, which is free for the amount of usage you incur here. The command also creates an associated Azure Application Insights instance in the same resource group, with which you can monitor your function app and view logs. For more information, see Monitor Azure Functions. The instance incurs no costs until you activate it.

[!INCLUDE functions-publish-project-cli]

Because your function uses an HTTP trigger and supports GET requests, you invoke it by making an HTTP request to its URL. It's easiest to do this in a browser.

Copy the complete Invoke URL shown in the output of the publish command into a browser address bar. When you navigate to this URL, the browser should display similar output as when you ran the function locally.

[!INCLUDE functions-streaming-logs-cli-qs]

[!INCLUDE functions-cleanup-resources-cli]

[!div class="nextstepaction"] Connect to Azure Cosmos DB [!div class="nextstepaction"] Connect to Azure Queue Storage