Creating Self Documenting Azure Functions with C# and OpenAPI: Part Three

When migrating existing business services to Azure PaaS as part of an App Modernization project, you may find yourself seriously considering serverless computing using Azure Functions, especially if your target architecture includes MicroServices.

Azure Functions let you focus on what counts — your requirements, your time, and your code — and less about boilerplate code, infrastructure, and processes.

When creating new APIs in any technology, one thing is essential: Documenting those APIs so that others can use them. This is especially important in large enterprises or situations where you are exposing these APIs to the public.

This blog series guides you through creating a C# Function App, creating self-documenting APIs, ensuring the quality of that generated documentation, and separating documentation based on the audience.

The blog post assumes the following:

  • You are familiar with C#
  • You know software development fundamentals
  • You are comfortable with command-line interfaces
  • You have completed Part Two of this series

At AIS, we’ve determined that one of the best approaches to documenting your APIs is to use OpenAPI (formerly Swagger) to have the APIs (nearly) document themselves. This saves time in the long run and enables API clients to generate client code to interact with your APIS automatically. In addition, this helps with a shelf life – if six months or a year down the road, we decide a better approach is best.

For these articles, I will walk you through the steps for creating well-documented Azure Functions for our fictitious shopping site called “Bmazon” and its modernization effort.

This is the final post in this series.

We Need to Lock it Down

In the previous article, we increased the quality of our OpenAPI spec by adding various C# attributes and XML comments to the mix. This resulted in a very useful and informative OpenAPI spec being generated.

Now, it turns out that our Security Team alerted us that some folks in the Warehouse were using their knowledge and access to the “Create Order” API to generate fake orders for themselves. This is a problem, and they have now updated the Security Procedures to require restricting people to the API calls they are supposed to use.

Currently, we have the following functions and departments that need to access them:

Function Description Shopping Department Warehouse
Create Order Creates an order to send to the Warehouse
Order Shipped Shipment update from the Warehouse to the System
Get Shipping Status Gets the current shipping status of an order

We have two Clients (Shopping Dept and Warehouse) that each need access to two functions.
We need to separate these things into two groups.

Put Functions In Groups

Swashbuckle supports putting things in Groups by using the ApiExplorerSettings attribute from Microsoft.AspNetCore.Mvc namespace. This attribute can be applied more than one time, so we can add these for all the functions like this:

Unfortunately, since you can’t use more than one ApiExplorerSettings attribute per function, we will need three groupings for this, “Warehouse,” “Shopping,” and “Shared,” to handle the method that was shared between. Therefore we’ll include the “Shared” method in all Swagger Documents generated.

[ApiExplorerSettings(GroupName = "Warehouse")]
[FunctionName("OrderShipped")]
public async Task<IActionResult> Run(
//...

[ApiExplorerSettings(GroupName = "Shopping")]
[FunctionName("CreateOrder")]
public async Task<IActionResult> Run(
//...

[ApiExplorerSettings(GroupName = "Shared")]
[FunctionName("OrderShippingStatus")]
public async Task<OrderShippingInfo> Run(
//...

By itself, putting them into these groups will not separate things into separate documents for you. It will just add a group name to the API method. For example, in the UI this renders like this:

Swagger UI showing groups for APIs

Create Separate API Specs

To create separate specs, you need to configure Swashbuckle to generate multiple documents and show it how to divide up the methods.

Configure the documents

Back to Startup.cs, we update the configuration with this:

builder.AddSwashBuckle(Assembly.GetExecutingAssembly(), opts =>
{
  // incorporate the XML documentation
  opts.XmlPath = "Bmazon.xml";

  // set up an "Everything" document and 2 documents with the 
  // same names as the group names used in the code
  opts.Documents = new SwaggerDocument[] {
    new SwaggerDocument()
    {
      Name = "Everything",
      Title = "Bmazon Shopping API",
      Description = "All APIs",
      Version = "1.0"
    },
    new SwaggerDocument()
    {
      Name = "Shopping",
      Title = "Bmazon Shopping API",
      Description = "API for the Shopping Department",
      Version = "1.0"
    },
    new SwaggerDocument()
    {
      Name = "Warehouse",
      Title = "Bmazon Warehouse API",
      Description = "API for the Bmazon Warehouse",
      Version = "1.0"
    }
  };
  //...

We now have one “Everything” that we’ll use as a default and two others that will be used for their respective clients.

Let’s configure Swashbuckle, so it knows what APIs to put in which documents.

Update the OpenAPI Functions to support individual API Specs

In that same method in the Startup, we also need to add the following:

opts.ConfigureSwaggerGen = genOpts =>
{
  // configure the separate document inclusion logic
  genOpts.DocInclusionPredicate((docName, apiDesc) =>
  {
    // generating the "everything" doc? then include this method
    if (docName == "Everything")
      return true;

    if (!apiDesc.TryGetMethodInfo(out MethodInfo methodInfo))
      return false;

    // get the value of the [ApiExplorerSettings(GroupName= "foo")]
    var attr = methodInfo.GetCustomAttributes(true)
      .OfType<ApiExplorerSettingsAttribute>().FirstOrDefault();

    var groupName = attr?.GroupName;

    // always return it if it's shared. Otherwise compare doc names
    return groupName == "Shared" || groupName == docName;
  });
};

Add Function Support For Selecting A Group

To allow the clients to select a specific group, we need to modify the JSON and UI OpenAPI functions to support selecting a group.

To do this, we add a new parameter to the JSON and UI Functions called “group” (defaulting to “Everything”)

/// <summary>
/// function implementation
/// </summary>
/// <param name="req">the http request</param>
/// <param name="swashbuckleClient">the injected Swashbuckle client</param>
/// <param name="group">the document to get (default: "Everything")</param>
/// <returns>the JSON data as an http response</returns>
[SwaggerIgnore]
[FunctionName(nameof(OpenApiJson))]
public static Task<HttpResponseMessage> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "openapi/json/{group?}")]
    HttpRequestMessage req,
    [SwashBuckleClient] ISwashBuckleClient swashbuckleClient,
    string group)
{
  return Task.FromResult(swashbuckleClient
    .CreateSwaggerJsonDocumentResponse(req, group ?? "Everything"));
}

/// <summary>
/// the function implementation
/// </summary>
/// <param name="req">the http request</param>
/// <param name="swashbuckleClient">the injected Swashbuckle client</param>
/// <param name="group">the optional document from the URL (default: "Everything")</param>
/// <returns>the HTML page as an http response</returns>
[SwaggerIgnore]
[FunctionName(nameof(OpenApiUi))]
public static Task<HttpResponseMessage> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "openapi/ui/{group?}")]
    HttpRequestMessage req,
    [SwashBuckleClient] ISwashBuckleClient swashbuckleClient,
    string group)
{
  // the CreateSwaggerUIResponse method generates the HTTP page from the JSON Function results
  return Task.FromResult(swashbuckleClient.CreateSwaggerUIResponse(
    req, $"openapi/json/{group ?? "Everything"}"));
}

Now, when you run the functions, you will have the option to have separate API specs for each Client by appending the document name to the URL, like “http://localhost:7071/api/openapi/ui/Shopping”, so that they will only know about the APIs they can call. To further lock this down, you can add authorization to the specific endpoints at a later time, possibly with Azure API Management.

Swagger UI showing the shopping APIs

Swagger UI showing the Warehouse APIs

In the future, rather than using security through obscurity, you can import these separate OpenAPI JSON files into Azure API Management to lock down the individual APIs by client, but we’ll leave that as an exercise for the reader.

Conclusion

Now that you have gone through these three articles, you have self-documenting APIs separated into different groupings that you can expose to individual clients. All you need to do is properly comment your code and decorate the Functions with the proper Attributes and you and your clients will be very satisfied.

Get the completed code from GitHub

When migrating existing business services to Azure PaaS as part of an App Modernization project, you may find yourself seriously considering serverless computing using Azure Functions, especially if your target architecture includes MicroServices.
Azure Functions let you focus on what counts — your requirements, your time and your code — and less about boilerplate code, infrastructure and processes.

When creating new APIs in any technology, one thing is very important: Documenting those APIs so that others can use them. This is especially important in large enterprises or situations where you are exposing these APIs to the public.

This blog series guides you through creating a C# Function App, creating self-documenting APIs, ensuring the quality of that generated documentation, and separating documentation based on the audience.

The blog post assumes the following:

  • You are familiar with C#
  • You have knowledge of software development fundamentals
  • You have completed Part One of this series

At AIS, we’ve determined that the one of the best approaches to documenting your APIs is to use OpenAPI (formerly Swagger) to have the APIs (nearly) document themselves. This saves time in the long run and even enables API clients to automatically generate client code to interact with your APIS. This helps with shelf life – if 6 months or a year down the road, we decide a better approach is best.

For these articles, I will walk you through the steps for creating well-documented Azure Functions for our fictitious shopping site called “Bmazon” and its modernization effort.

We Need Better Documentation

In the Previous Post, we got the Azure Functions application to start generating OpenAPI docs for our functions, but the results were somewhat underwhelming:

Swagger UI page for the CreateOrder operation showing very little detail

Here you can see that, even though the CreateOrder call takes an Order object in the body of the HTTP Post, there is no documentation describing this. This is because, unlike when writing traditional dotnet core APIs, the order is not a parameter to the function. Swashbuckle only has access to the function signature and anything that can be discovered through reflection.

This output is not very helpful to our clients. They need to know our inputs, potential HTTP Codes to expect (it just assumes that it will return a 200), and other pertinent information like what the method does and what the return data will look like.

For instance, if we add data validation to this method, we may wind up returning a 400 (Bad Request). We could also possibly return a 409 (Conflict) if the order already exists.

Since you’re reading this, you know there is a way to do this. Let’s get to it.

Give Swashbuckle More Info

In order for the OpenAPI documentation to be much better, we need to add a few things that Swashbuckle will be able to use to generate the docs.

As I stated previously, Swashbuckle only has access to things that can be discovered through reflection, which means the definition of your function, its parameters and any attributes decorating it, so the following translates to very little information.

[FunctionName("CreateOrder")]
public async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "order")]
    HttpRequestMessage req,
    ILogger log)

This doesn’t even have any information about the Order type that is expected in the body of the method, never mind return codes.

Expected Body Type

To document the type expected in the body of the POST, we need to tell Swashbuckle what to expect. We do this by using the RequestBodyType attribute from the AzureFunctions.Extensions.Swashbuckle.Attribute namespace.

Note that this is an additional attribute on the req parameter on top of the existing HttpTrigger attribute.

[FunctionName("CreateOrder")]
public async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "order")]
    [RequestBodyType(typeof(Order), "The Order To Create")] // Describes the Body
    HttpRequestMessage req,
    ILogger log)

With this in place, Swashbuckle knows what type the body contains and we now see that the body type is present in the UI:

The Create Order Swagger UI with body type specified

If you click on the “Schema” link, you will even see the data type names being used:

Create Order Swagger UI showing Schema of the Order type

Note that the Items array is marked nullable: true which is not desirable. We will address that below in the Data Annotations section.

The bottom of the page also shows you all the current objects in the Schema that are known:

Swagger UI with the all Schemas

This information documents all the details about the DTOs being used in this API. But we need to fix the nullability and other validation-related information.

Add Data Annotations

Above, the Order‘s Items collection was marked as nullable. We want to fix that and other validation information that Swashbuckle can read. To do that, we need to add Data Annotations to the object definitions.

Currently, the Order looks like this:

public class Order
{
  public int OrderId { get; set; }
  public IEnumerable<OrderLineItem> Items { get; set; }
}

In order to tell Swashbuckle (and our clients) that the Items collection is required, we have to mark it [Required] and [NotNull] from the System.Diagnostics.CodeAnalysis namespace.

The NotNull attribute is also needed because OpenAPI, not being language-specific, supports the concept of null along with the lack of presence of the variable. JavaScript developers will relate to this concept with undefined and null keywords.

So, in order to tell clients that fields MUST have a value, you need to add both attributes to the Items property.

  public class Order
  {
    public int OrderId { get; set; }

    [Required, NotNull]
    public IEnumerable<OrderLineItem> Items { get; set; }
  }

The results:

Create Order Swagger UI with corrected Required fields

Note the red "*", meaning required, next to the items collection and the lack of the nullable:true.

To properly annotate the objects, we’ll mark the ID, Quantity and SKU all required as well. Additionally, we’ll put rational [Range] and other appropriate restrictions as well:

public class Order
{
  // if we get to 2 billion orders, we'll all be retired anyway
  [Required, NotNull, Range(1, int.MaxValue)]
  public int OrderId { get; set; }

  [Required, NotNull, MinLength(1)]
  public IEnumerable<OrderLineItem> Items { get; set; }
}

public class OrderLineItem
{
  [Required, NotNull, Range(1, 1000)]
  public int Quantity { get; set; }

  [Required, NotNull, MinLength(1)]
  public string SKU { get; set; }
}

So, the final schema looks like this:
Create Order Swagger UI with Full data annotations

Now your clients know the simple data validations for these objects, but don’t know what the return payloads and HTTP codes are.

Potential Return Types and Codes

By default, Swashbuckle will tell the clients to expect a 200 (Success) HTTP result with no payload.

Swagger UI showing only a 200 response

This doesn’t include any information about any payload sent back to the user and is most likely incorrect or at least not the whole story.

If we know our Function is going to return multiple HTTP codes with different payloads, we need to tell Swashbuckle by using the [ProducesResponseType] attribute on the Function itself.

Assuming we return the following:

  • 200/Success with a string message payload
  • 400/BadRequest with a collection of error messages

We decorate our function like this:

[ProducesResponseType(typeof(string), StatusCodes.Status200OK)]
[ProducesResponseType(typeof(IEnumerable<string>), StatusCodes.Status400BadRequest)]
HttpStatusCode.BadRequest)]
[FunctionName("CreateOrder")]
public async Task<IActionResult> Run(

This results in

Swagger UI - multiple response types with http codes

So, we’ve now exposed the input and output types, but we haven’t been able to add any additional information to describe objects or fields to our clients. To do that, we need to add XML comments to the output as well.

To make this information even better, we can comment our code properly. Of course, you were already doing that, right? RIGHT?

Better Comments in the OpenAPI Spec

One thing that you may notice is that, at the top of the function, there is very little information about the method except the name (e.g. “CreateOrder”). We should add a summary about the method.

Now, I need to apologize because I lied to you. Previously, when I said “Swashbuckle only has access to things that can be discovered through reflection”, I was lying (Forgive me!). To give client devs more information about the methods being exposed by an API, we can add C# XML Documentation information to the code and, if configured for it, Swashbuckle will incorporate that too, which can be invaluable.

Add XML Comments

We now add comments like this to our C# code (Functions and DTOs)

/// <summary>
/// Creates an Order that will be shipped to the Warehouse for fulfillment.
/// </summary>
/// <param name="req">the HTTP request</param>
/// <param name="log">the logger</param>
/// <returns>a success message or a collection of error messages</returns>
/// <response code="200">
///   Indicates success and returns a user-friendly message
/// </response>
/// <response code="400">
///   Indicates a data validation issue and will return a list of data validation errors
/// </response>
[ProducesResponseType(typeof(string), StatusCodes.Status200OK)]
[ProducesResponseType(typeof(IEnumerable<string>), StatusCodes.Status400BadRequest)]
HttpStatusCode.BadRequest)]
[FunctionName("CreateOrder")]
public async Task<IActionResult> Run() {
// ...
}

/// <summary>
/// An Order sent from the Shipping Division to be sent to the Warehouse
/// </summary>
public class Order
{
//...
}

The Swagger UI won’t have changed yet. In order for the Swashbuckle library to read this information, you need to tell the C# compiler to generate the documentation in an XML file and tell Swashbuckle about it.

Generate XML Doc file

At the top of the csproj file, add the following line to the first <PropertyGroup> you see.

<DocumentationFile>Bmazon.xml</DocumentationFile>

If you are using Visual Studio, you can access this setting from the Build tab on the Project settings

Now tell Swashbuckle about the XML file

Currently, we’re configuring Swashbuckle in the StartUp.cs file with:

builder.AddSwashBuckle(Assembly.GetExecutingAssembly());

Replace this with

builder.AddSwashBuckle(Assembly.GetExecutingAssembly(), opts => {
  opts.XmlPath = "Bmazon.xml";
});

Now, when you rerun the app, the final result will be a page with the new title and the order schema will have much more detail.

Swagger UI showing Create Order Scheme with XML comment information

The users of your service will thank you for documenting your APIs this thoroughly. Additionally, they won’t have to ask you questions about the details about how to use the APIs. They can even generate client code with various tools as well.

Get the completed code from GitHub

Next Steps

Now that you have really descriptive documentation for your APIs being automatically generated, your security folks may not like you sending all your API documentation to every single client, regardless of need.

In part three of the series, I will show you how to separate the APIs out into separate groupings and keep your clients all in their own lane.

TOP MODERNIZATION APPROACHES
Learn about the top three modernization approaches — rehosting, replatforming, and refactoring — uncovering pros, cons, and process ideas as you go.

When migrating existing business services to Azure PaaS as part of an App Modernization project, you may find yourself seriously considering serverless computing using Azure Functions, especially if your target architecture includes MicroServices.

Azure Functions let you focus on what counts — your requirements, your time, and your code — and less about boilerplate code, infrastructure, and processes.

When creating new APIs in any technology, one thing is very important: Documenting those APIs so that others can use them. This is especially important in large enterprises or situations where you are exposing these APIs to the public.

This blog series guides you through creating a C# Function App, creating self-documenting APIs, ensuring the quality of that generated documentation, and separating documentation based on the audience.

The blog series assumes the following:

  • You are familiar with C#.
  • You have knowledge of software development fundamentals.
  • You are comfortable with command-line interfaces.

At AIS, we’ve determined that one of the best approaches to documenting your APIs is to use OpenAPI (formerly Swagger) to have the APIs (nearly) document themselves. This saves time in the long run and even enables API clients to automatically generate client code to interact with your APIs. This helps with shelf life – if 6 months or a year down the road, we decide a better approach is best.

For these articles, I will walk you through the steps for creating well-documented Azure Functions for our fictitious shopping site called “Bmazon” and its modernization effort.

Creating the App

To create the app, we will start with the Azure Functions Core Tools. At the time of this writing, the current version of this library is 3.0.3477

NOTE: This version uses dotnet cli version 3.1 internally, so if your dotnet executable in the path is not that version, it could cause you issues. If you run into errors, this may be fixed by adding global.json file in the current directory with the following content, which will tell the dotnet cli to use whatever 3.1.x version you have installed.

{
  "sdk": {
    "version": "3.1.0",
    "rollForward": "latestMinor"
  }
}

At the PowerShell prompt, we’ll run the following to create our project

C:\dev> func --version
3.0.3477
C:\dev> func init Bmazon --worker-runtime dotnet

Writing C:\dev\Bmazon\.vscode\extensions.json

This will create the shell of a project inside the C:\dev\Bmazon folder.

While creating the app, I’ve copied in an OrderService and the related DTOs from the existing application we’re modernizing to be used by the newly new functions we are creating. You can see the completed code on GitHub. You’ll see a bit more of them in the next article.

Learn more about Azure Functions From Microsoft Docs

Add Functions

We’re going to add 3 different functions to our app.

Shopping API

The Shopping division needs to call HTTP APIs to make an order to the warehouse, so we will add a CreateOrder function that performs this action.

(This can be done interactively by running func new and following prompts, but using the command line parameters is more concise.)

C:\dev\Bmazon> func new --template HttpTrigger --name CreateOrder `
    --authlevel Anonymous
Use the up/down arrow keys to select a template:Function name: CreateOrder

The function "CreateOrder" was created successfully from the 
"HTTPTrigger" template.

Strangely, it outputs a prompt to select the template even when you have passed in the selection as a parameter. You can ignore this.

Warehouse API

Later in our process, the Warehouse team needs to call an HTTP endpoint to send tracking information back to the Shopping division.

We will follow the pattern above and create an API for them to call.

C:\dev\Bmazon> func new --template HTTPTrigger --name OrderShipped `
    --authlevel Anonymous
Use the up/down arrow keys to select a template:Function name: OrderShipped

The function "OrderShipped" was created successfully from the 
"HTTPTrigger" template.

Shared APIs

Since both the Shopping and Warehouse divisions will need to check on the status of an order at various times, there will be a shared function to check status.

C:\dev\Bmazon> func new --template HTTPTrigger --name OrderShippingStatus `
    --authlevel Anonymous
Use the up/down arrow keys to select a template:Function name: OrderShipped

The function "OrderShippingStatus" was created successfully from the 
"HTTPTrigger" template.

Code Cleanup

We’ll do a bit of code cleanup before moving on.

Choose GET or POST

If you look at the code, you’ll notice that, by default, the Functions were created supporting both GET and POST.

public async Task<IActionResult> Run(
   [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)]
   HttpRequest req
...

We can fix that by changing the code on each function by removing either "get" or "post" appropriately (Typically you will have the first 2 operations be POSTs and the latter be GET).

Organizing the Code

The func calls above will create all the Function files in the top folder. We’ll move ours into a Functions folder to keep things cleaner. They all just happened to start with “O”, so we can be terse.

C:\dev\Bmazon> mkdir Functions; mv O*.cs Functions\

Add OpenAPI Document Generation

In order to add OpenAPI to Azure Functions, I chose to use the Swashbuckle library. There are a few other libraries out there to work with .Net and OpenAPI, but I chose Swashbuckle because I’m familiar with it.

Installing the Package

The core Swashbuckle project doesn’t support Azure Functions directly, so I used the AzureExtensions.Swashbuckle package, a nice extension written by Vitaly Bibikov.

To install it:

C:\dev\Bmazon> dotnet add package AzureExtensions.Swashbuckle

  Determining projects to restore...
  Writing C:\Users\XXX\AppData\Local\Temp\tmp69AA.tmp
info : Adding PackageReference for package 'AzureExtensions.Swashbuckle' into project 'C:\dev\Bmazon\Bmazon.csproj'.
info : Restoring packages for C:\dev\Bmazon\Bmazon.csproj...
...
...
info : Committing restore...
info : Generating MSBuild file C:\dev\Bmazon\obj\Bmazon.csproj.nuget.g.props.
info : Writing assets file to disk. Path: C:\dev\Bmazon\obj\project.assets.json
log  : Restored C:\dev\Bmazon\Bmazon.csproj (in 525 ms).

Setting up Swashbuckle

In order to configure Swashbuckle, your Functions App needs a Functions Startup class like the following, which we’ll put in Startup.cs in the Bmazon folder.

using System.Reflection;
using AzureFunctions.Extensions.Swashbuckle;
using Microsoft.Azure.Functions.Extensions.DependencyInjection;

[assembly: FunctionsStartup(typeof(Bmazon.Startup))]
namespace Bmazon
{
  public class Startup : FunctionsStartup
  {
    public override void Configure(IFunctionsHostBuilder builder)
    {
      builder.AddSwashBuckle(Assembly.GetExecutingAssembly());
    }
  }
}

Exposing OpenAPI Endpoints

Your code will also need to expose the OpenAPI JSON and UI endpoints as HTTP-triggered Azure Functions so that client code can load them on demand.

(Adding them in a single OpenApi\OpenApiFunctions.cs file for now)

using System.Net.Http;
using System.Threading.Tasks;
using AzureFunctions.Extensions.Swashbuckle;
using AzureFunctions.Extensions.Swashbuckle.Attribute;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;

namespace Bmazon.OpenApi
{
  public static class OpenApiFunctions
  {
    [SwaggerIgnore]
    [FunctionName("OpenApiJson")]
    public static Task<HttpResponseMessage> RunJson(
        [HttpTrigger(
            AuthorizationLevel.Anonymous, 
            "get", Route = "openapi/json")]
        HttpRequestMessage req,
        [SwashBuckleClient] ISwashBuckleClient swashbuckleClient)
    {
      return Task.FromResult(
            swashbuckleClient.CreateSwaggerJsonDocumentResponse(req));
    }

    [SwaggerIgnore]
    [FunctionName("OpenApiUI")]
    public static Task<HttpResponseMessage> RunUi(
        [HttpTrigger(
            AuthorizationLevel.Anonymous, 
            "get", 
            Route = "openapi/ui")]
        HttpRequestMessage req,
        [SwashBuckleClient] ISwashBuckleClient swashbuckleClient)
    {
      // CreateOpenApiUIResponse generates the HTML page from the JSON results
      return Task.FromResult(
            swashbuckleClient.CreateSwaggerUIResponse(req, "openapi/json"));
    }
  }
}

This sets up 2 new Functions on the openapi/json and openapi/ui URLs to load the JSON file and Swagger UI respectively. The [SwaggerIgnore] attribute causes Swashbuckle to ignore these API methods for document generation purposes.

Generate and View the API Documentation

NOTE: You must have the Azure Storage Emulator or Azurite RUNNING locally in order for this to work properly.

C:\dev\Bmazon> func start
Microsoft (R) Build Engine version 16.8.3+39993bd9d for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored C:\dev\Bmazon\Bmazon.csproj (in 840 ms).
  Bmazon -> C:\dev\Bmazon\bin\output\bin\Bmazon.dll

Build succeeded.

Time Elapsed 00:00:05.60

Azure Functions Core Tools
Core Tools Version:       3.0.3284 Commit hash: 98bc25e668274edd175a1647fe5a9bc4ffb6887d
Function Runtime Version: 3.0.15371.0

[2021-02-27T15:05:33.871Z] Found C:\dev\Bmazon\Bmazon.csproj. Using for user secrets file configuration.

Functions:

  CreateOrder: [POST] http://localhost:7071/api/order
  OpenApiJson: [GET] http://localhost:7071/api/openapi/json
  OpenApiUi: [GET] http://localhost:7071/api/openapi/ui
  OrderShipped: [POST] http://localhost:7071/api/order/shipment
  OrderShippingStatus: [GET] http://localhost:7071/api/order/shipment/{id}

For detailed output, run func with --verbose flag.
[2021-02-27T15:05:41.693Z] Host lock lease acquired by instance ID '000000000000000000000000016514FF'.

If you don’t see that last line after a few seconds, you probably don’t have the storage emulator running

Take note of the list of functions shown with the URLs next to them, especially the ones starting with “OpenApi”.

If you visit the OpenApiUI URL listed above, you will see the following in your browser:

Rendered Swagger UI displaying the 3 created Operations

That’s it! You now have a modernized serverless architecture with APIs that are documenting themselves!

If you add any new Functions, they will automatically show up here as well. Your clients can download from the JSON endpoint and import the definitions into Postman or client generators.

Get the completed code from GitHub

Next Steps

Now that you have self-documenting APIs, you may notice that the information in the Swagger UI is rather underwhelming. Due to the nature of Azure Functions, there is very little information that Swagger can glean from the runtime type information it can gather.

In part two of the series, I will show you how to make the documentation MUCH better.

TOP MODERNIZATION APPROACHES
Learn about the top three modernization approaches — rehosting, replatforming, and refactoring — uncovering pros, cons, and process ideas as you go.

If you want to create robust automated workflows in Azure, integrating Azure Logic Apps with Azure Functions can be a valuable solution. A logic app is a PaaS (Platform as a Service) that offers extensive options to create powerful workflows. This service is beneficial if you need a structured series of events to support your Azure-hosted application(s). To craft workflows, you can use a “no-code” method. Azure Logic Apps offers a graphical user interface approach to creating workflows, which bridges the gap between pairing your other Azure applications with your logic app.

Why Integrate?

One of the big reasons to integrate these two services is to help support a systematic end-to-end solution. You can add your essential function(s) to your workflow in a few steps, hence creating a more robust cloud-based solution.

When your workflow process gets triggered, such as an email reaching an inbox, your Azure Function can perform its specific business logic after the trigger fully executes. Then, the workflow can branch-off and perform more actions.

Using Azure Functions in your workflow also allows you to capture the HTTP status code from the resulting function call. If receiving a specific status code, such as an HTTP 500 status code, there can be logic in place to email support personnel to inform them, or the results of the failed function call can be inserted into Azure Storage. There are many possibilities.

Getting Started

When beginning integrating an Azure Function into a logic app, there are a few prerequisites. You will need to create both a logic app and function service in Azure. I will be using the out-of-the-box HTTP trigger Azure Function from Visual Studio, and it will simply return “Hello World” when it receives a request. Once the Azure Function service has been created, and the code deployed to it, the next area of focus is setting up the logic app workflow.

Setting up the Logic App Workflow

There are two ways to set up a workflow; the first is an infrastructure as code (IaC) approach, and the second is a GUI approach. For this walkthrough, I will use the GUI. The first thing you will need for the logic app is a trigger. This is an event that starts your logic app workflow. Many distinct types of triggers help us carry out many tasks. I will be using the timer trigger for this example.

Notification Frequency in Logic Apps

After you have published your code to your Azure Function, you will be able to add it as an Azure Function action. One thing to note about the Azure Function action is that it takes care of your function’s authentication. So, if your endpoint has a function authorization level assigned, the action will take care of authenticating so you can use the function in your workflow. Now, once the trigger activates, it will call the Azure Function. From there, it is up to the function to handle the request.

Azure Function Request

The Azure Function will process the request and fetch the correct data for the rest of the workflow to process. The next step will be to create a condition action. This will run as a conventional if statement. After the Azure Function executes a request, we want to verify if the request was successful or not.

What is neat about using logic apps is that when you use a service, like an Azure Function, it will detect specific properties from the service to use in later actions. For the condition action, we can grab the response status code of the function that just ran. Using that status code, we can create custom logic to look for the necessary code numbers. For this action, we will check for an HTTP 200 status code. When you create a condition, it automatically generates true and false scenarios. From there, you can set up what happens during each scenario.

For the following steps, we will set up one of my favorite parts of using a logic app that integrates with Outlook! There are many various tasks to use for Outlook. For this example, we will be using the send email task.

Send Email Task Outlook Task

When you set up an Outlook task, you must first log in with your desired Outlook account. This will produce an office365 API connection resource in your resource group. Thus, allowing the logic app workflow to work properly with Outlook!

After you log in, you can start using Outlook tasks. For this part of the workflow, we are going to send an email to the recipient. In the body of the email, we will send the response we get from the Azure Function we called in an earlier step. However, if the Azure Function call fails, then we can return a default email message to the recipient.

Azure Function Email Send

This concludes the setup for the Azure Logic App workflow that now integrates with an Azure Function. To run your newly created workflow, simply navigate to the “Overview” tab of your logic app resource. From there, click on “Run Trigger.”

Email Send Failure Function in Outlook

Congratulations! Your new workflow is now ready to run.

After the timer interval has passed, you will find a new email in your inbox from the Azure Logic App workflow.

Closing Thoughts

The beauty of using Azure Logic Apps is the customizability that it provides. The possibilities are almost endless. Whether your workflow is simple or complex, you have the tools at your disposal to carry out your systematic end-to-end flow. This post shows you one flavor of logic apps and the type of workflow you can create.

“How does one choose between all the various PaaS options available in Azure?”

This question comes up very often at conferences and forums. The answer, as you might have guessed, is “it depends…”

In this blog post, however, we will go beyond “it depends” and try to describe some factors that can help you choose between the full Azure PaaS service list offerings.

(Not sure what PaaS is in Azure or how they relate?. If not, please briefly review my introductory blog post on PaaS.)

Let’s get started. We will cover the following Azure PaaS cloud service offerings:
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