Quickstart: Create a C# function in Azure from the command line

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

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

There is also a Visual Studio Code-based version of this article.

Configure your local environment

Before you begin, you must have the following:

Prerequisite check

Verify your prerequisites, which depend on whether you are using Azure CLI or Azure PowerShell for creating Azure resources:

  • In a terminal or command window, run func --version to check that the Azure Functions Core Tools are version 3.x.

  • Run az --version to check that the Azure CLI version is 2.4 or later.

  • Run az login to sign in to Azure and verify an active subscription.

  • Run dotnet --list-sdks to check that .NET Core SDK version 3.1.x is installed

Create a local function project

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 --dotnet
    
  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 a HttpExample.cs code file.

(Optional) Examine the file contents

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

HttpExample.cs

HttpExample.cs contains a Run method that receives request data in the req variable is an HttpRequest that's decorated with the HttpTriggerAttribute, which defines the trigger behavior.

using System;
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;

namespace LocalFunctionProj
{
    public static class HttpExample
    {
        [FunctionName("HttpExample")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req,
            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;

            return name != null
                ? (ActionResult)new OkObjectResult($"Hello, {name}")
                : new BadRequestObjectResult("Please pass a name on the query string or in the request body");
        }
    }
}

The return object is an ActionResult that returns a response message as either an OkObjectResult (200) or a BadRequestObjectResult (400). To learn more, see Azure Functions HTTP triggers and bindings.

Run the function locally

  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 below, 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 append the query string ?name=<YOUR_NAME>, making the full URL like http://localhost:7071/api/HttpExample?name=Functions. The browser should display a message like Hello Functions:

    Result of the function run locally in the browser

  3. The terminal in which you started your project also shows log output as you make requests.

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

Create supporting Azure resources for your function

Before you can deploy your function code to Azure, you need to create three resources:

  • A resource group, which is a logical container for related resources.
  • A Storage account, which maintains state and other information about your projects.
  • A function app, which provides the environment for executing your function code. A function app maps to your local function project and lets you group functions as a logical unit for easier management, deployment, and sharing of resources.

Use the following commands to create these items. Both Azure CLI and PowerShell are supported.

  1. If you haven't done so already, sign in to Azure:

    az login
    

    The az login command signs you into your Azure account.

  2. Create a resource group named AzureFunctionsQuickstart-rg in the westeurope region:

    az group create --name AzureFunctionsQuickstart-rg --location westeurope
    

    The az group create command creates a resource group. You generally create your resource group and resources in a region near you, using an available region returned from the az account list-locations command.

  3. Create a general-purpose storage account in your resource group and region:

    az storage account create --name <STORAGE_NAME> --location westeurope --resource-group AzureFunctionsQuickstart-rg --sku Standard_LRS
    

    The az storage account create command creates the storage account.

    In the previous example, replace <STORAGE_NAME> with a name that is appropriate to you and unique in Azure Storage. Names must contain three to 24 characters numbers and lowercase letters only. Standard_LRS specifies a general-purpose account, which is supported by Functions.

  1. Create the function app in Azure:

    az functionapp create --resource-group AzureFunctionsQuickstart-rg --consumption-plan-location westeurope --runtime dotnet --functions-version 3 --name <APP_NAME> --storage-account <STORAGE_NAME>
    

    The az functionapp create command 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 provisions 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.

Deploy the function project to Azure

After you've successfully created your function app in Azure, you're now ready to deploy your local functions project by using the func azure functionapp publish command.

In the following example, replace <APP_NAME> with the name of your app.

func azure functionapp publish <APP_NAME>

The publish command shows results similar to the following output (truncated for simplicity):

...

Getting site publishing info...
Creating archive for current directory...
Performing remote build for functions project.

...

Deployment successful.
Remote build succeeded!
Syncing triggers...
Functions in msdocs-azurefunctions-qs:
    HttpExample - [httpTrigger]
        Invoke url: https://msdocs-azurefunctions-qs.azurewebsites.net/api/httpexample

Invoke the function on Azure

Because your function uses an HTTP trigger, you invoke it by making an HTTP request to its URL in the browser or with a tool like curl.

Copy the complete Invoke URL shown in the output of the publish command into a browser address bar, appending the query parameter &name=Functions. The browser should display similar output as when you ran the function locally.

The output of the function run on Azure in a browser

Run the following command to view near real-time streaming logs:

func azure functionapp logstream <APP_NAME> 

In a separate terminal window or in the browser, call the remote function again. A verbose log of the function execution in Azure is shown in the terminal.

Clean up resources

If you continue to the next step and add an Azure Storage queue output binding, keep all your resources in place as you'll build on what you've already done.

Otherwise, use the following command to delete the resource group and all its contained resources to avoid incurring further costs.

az group delete --name AzureFunctionsQuickstart-rg

Next steps