Adding Business Logic to Azure Logic App with Azure API App

I hope you had a chance to watch or attend AzureCon lately. If you watch the keynotes, you would be overwhelmed by tons of great announcements that were made. All the sessions are available on demand and are classified by level and industry role. I hope the sessions prove to be a great learning experience for you. I also hope to work with a few of the new features and write about them for us to use.

What I would like to discuss today is about a nifty feature of Logic App.  You can extend your Logic App workflow by adding Web APIs or API Apps in it. This feature gives you complete control over your application business logic and gives you freedom to only write code for any custom transformation or data manipulation which might not be available out of the box and rely on the various Logic App connectors for the rest of the data flow. This combination of Logic App connectors (which are actually API Apps) and your own API Apps can solve many integration scenarios.

What are Logic Apps?

In day to day scenario applications just orchestrate data. Logic Apps are a mechanism to automate business processes without requiring the developers to write code for such orchestrations. If you are familiar with BizTalk, you would find that Logic Apps are very similar to BizTalk orchestration. Just as you can use different shapes to create a business process workflow in BizTalk, so too you can use the connectors from the Marketplace or your own API Apps, represented graphically in Logic Apps, to create a workflow. Logic Apps allow developers to design workflows that start from a trigger and then execute a series of steps, each invoking an App Service API App whilst securely taking care of authentication and best practices like check pointing and durable execution.

In simple terms, Logic Apps are workflows that you can create in a graphical way to articulate business logic. Logic Apps can communicate with external systems to receive or send data or even trigger its execution. In essence, Logic App is an orchestration of various connectors and your own API Apps.

Let’s Build a Sample

I will demonstrate how you can extend a Logic App by adding your own API App to a Logic App. Although, we would be building a new API App in this sample, if you want to plug an existing Web API into your Logic App, you would need to follow the steps mentioned here.  Let’s build a sample that lists the files in One Drive root folder and sends an HTML formatted email to the user.

Create a Logic App and Add OneDrive Connector

From the Azure Management Portal, click + New at the bottom-left of the screen, expand Web + Mobile, then click Logic App. Supply the basic details required to create your App.

Create Logic App
Create Logic App - Full Image

Once your Logic App is created, open the Logic App that you just created and click on Edit to launch the designer blade.

Edit Logic App
Edit Logic App - Full Image

In the designer blade you would see options for creating a Logic App from the various templates provided by Microsoft. Click on Create from Scratch to launch an empty designer blade. The designer blade will have a Start Logic card by default. You may add a trigger to launch the Logic App workflow or execute it on demand. For the sample, check the Run the logic manually checkbox to make the logic execute on demand.

You will find API Apps that are available to you either because they are deployed in your subscription or because they are available from the Marketplace in the API Apps window on the right hand side of the designer. Add OneDrive connector from the Marketplace in your Logic App. The connector will ask you for your credentials and request for authorization the first time. Provide the necessary credentials to enable the connector. You can read more about OneDrive connector here. In the OneDrive connector card, select List Files action. You will be asked to provide path to a folder in the Folder Path field.The files inside this folder would be listed by the OneDrive connector. Type “/” for the root folder path in the Folder Path field. Click on the check mark to save your changes. At the end of the operation, you should be able to see the summary of the card. Click Save to save the workflow.

OneDrive Connector Summary
OneDrive Connector Summary - Full Image

Close the designer blade and execute the workflow at this point by clicking on Run Now to see if everything works fine till this point. You can get the response generated by executing this workflow from the All Runs tile inside your Logic App tile. Click on the relevant run and then on “microsoftonedriveconnector” to get the input and output of the connector. We will use this output to build our API App.

Create OneDrive Service API App

The complete code for the API App is available for download here.

In Visual Studio create a new API App from Web Project Template (requires Azure SDK).

API App Template Visual Studio
API App Template Visual Studio - Full Image

Add a new class OneDriveConnectorRequest in the Models folder and write the following code in it. As you might have already guessed, this is the same format in which OneDrive connector provides its output.

public class OneDriveConnectorRequest
    public string FileName { get; set; }
    public object FolderPath { get; set; }
    public object LastModifiedUtc { get; set; }
    public object FileSizeInBytes { get; set; }
    public string FilePath { get; set; }

Next, replace the template code in Values controller with the following code. This code will place the OneDrive connector output in a local variable and expose that data formatted as HTML for Office365 connector, which we will add soon.

public class ValuesController : ApiController
    private static OneDriveConnectorRequest[] files;

    // GET api/values
    public string Get()
        var data = "<h1>Files in Your OneDrive</h1>";
        foreach (var value in files)
            data += "<p>" + value.FileName + "</p>";

        return data;

    // POST api/values
    public void Post([FromBody]OneDriveConnectorRequest[] value)
        files = value;

Its time to publish your API. Right click on your project and click on Publish. Select Microsoft Azure API App from the menu and follow the steps to create a new API App and subsequently deploy the App to Azure.

API App Publish Dialog
API App Publish Dialog - Full Image

Once your API App gets published, navigate back to the Logic App workflow. You would find your App listed in the API App window.

Listed API Apps
Listed API Apps - Full Image

Click on your API App to add it to the workflow. Click on Values_PostByValue action. Your function expects data in the value parameter. Write@body(‘microsoftonedriveconnector’) in the text box to bind the input to OneDrive connector output. Click the check mark to save the changes.

Now add another card of your API App in the workflow. We will use this connector to query the data in the API App and bind its output to the Office 365 connector. Click on Values_Get and click the check mark to save the changes.

Add Office 365 Connector

Select Office365 Connector from the API Apps list. When the card gets added, it will ask for authorization. Provide your credentials to enable the connector (Tip: If you miss authorizing the connectors the first time, you can click on the three dots on the relevant connector tile and select Authorize this action and click on the Authorize button). Select Send Email action and fill the To and Subject field with the recipient’s email and subject message. In the Body field write @body(‘onedriveservice0’) (or whatever is the name of your second connector. You can get this field populated automatically by clicking on the three dots next to the parameter field). Click on the three dots in the parameter list to expand it. Find Is HTML parameter and set its value to true. Click on the check mark and then on Save to save the workflow. Now your workflow should look similar to the following.

Workflow - Full Image


Now the App is ready to be tested. Close the designer blade and click on Run Now to execute the Logic App. Following is the mail  that I received.

sample response
sample response - Full Image

I hope you liked building this. How was your experience working with Logic Apps? Let me know in the comments below. See you soon! Happy Exploring!

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Your 2 cents

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Hi! I'm Rahul Rai, an author, a programmer, and a technophile. I'm a Senior Consultant at Readify, Sydney, Australia.

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