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Design Wasabi Power Apps

This article shows how to gain real-time, database-like connectivity from mobile and tablet PowerApps.

Microsoft PowerApps provides a drag and drop interface, underpinned by a rich set of formulas, for generating mobile and tablet apps that are connected to data. The CData API Server, when paired with the ADO.NET Provider for Wasabi (or any of 160+ other ADO.NET Providers), extends PowerApps with connectivity to remote data sources, without a need to maintain a separate copy of the data in the PowerApps Common Data Service. The CData API Server provides database-like connectivity for Wasabi, augmenting the functionality of SaaS APIs and NoSQL databases with an in-memory SQL-92 engine.

The CData API Server also supports the Swagger metadata standard, whose UI-generation and code-generation possibilities are utilized across Azure App Service, Microsoft Flow, and PowerApps. With Swagger, PowerApps generates a complete set of formulas for working with Wasabi -- this article shows how to use these formulas to connect your PowerApp to remote Wasabi data.

Set Up the API Server

Follow the steps below to begin producing secure Wasabi OData services:

Deploy

The API Server runs on your own server. On Windows, you can deploy using the stand-alone server or IIS. On a Java servlet container, drop in the API Server WAR file. See the help documentation for more information and how-tos.

The API Server is also easy to deploy on Microsoft Azure, Amazon EC2, and Heroku.

Connect to Wasabi

After you deploy the API Server and the ADO.NET Provider for Wasabi, provide authentication values and other connection properties by clicking Settings -> Connections and adding a new connection in the API Server administration console. You can then choose the entities you want to allow the API Server access to by clicking Settings -> Resources.

To authorize Wasabi requests, provide the credentials for an administrator account or for an IAM user with custom permissions. Set AccessKey to the access key Id. Set SecretKey to the secret access key.

Note: You can connect as the AWS account administrator, but it is recommended to use IAM user credentials to access AWS services.

For information on obtaining the credentials and other authentication methods, refer to the Getting Started section of the Help documentation.

Authorize API Server Users

After determining the OData services you want to produce, authorize users by clicking Settings -> Users. The API Server uses authtoken-based authentication and supports the major authentication schemes. You can authenticate as well as encrypt connections with SSL. Access can also be restricted by IP address; Access is restricted to only the local machine by default.

You will also need to enable CORS and then define the following sections by clicking Settings -> Server. As an alternative, you can select the option to allow all domains without '*'.

  1. Access-Control-Allow-Origin: Set this to a value of '*', or the domains you will be calling the API Server from.
  2. Access-Control-Allow-Methods: Set this to a value of "GET,PUT,POST,OPTIONS", or the HTTP methods you will need to use.
  3. Access-Control-Allow-Headers: Set this to "x-ms-client-request-id, authorization, content-type".

Last, you will need to configure the API Server to allow users to authenticate by passing the authtoken as a part of the URL. To do so, navigate to the www/app_data folder in the installation direction and modify the settings.cfg file to add the following line in the [Application] section:

AllowAuthTokenInURL = true

Retrieve the Swagger Metadata

You will use the metadata to create a Custom API connection. You can obtain the Swagger definition by making the following request in your browser and then saving the resulting JSON file:

http://MySite:MyPort/api.rsc/$swagger

Connect to Wasabi Through the API Server

The following procedure shows how to create a simple app that searches remote Wasabi data.

  1. In Microsoft PowerApps, click Custom connectors.
  2. Click Create custom connector and choose Import an OpenAPI file.
  3. Name the connector, browse to the JSON file, and click Continue.
  4. Fill in the relevant General information, ensure that Base URL is of the form /api.rsc/@myauthtoken (where myauthtoken is the AuthToken for a configure API Server user), and click Continue.
  5. Select Basic authentication for the Authentication type and use the default Parameter labels and names. Click Continue.
  6. Review the Action and Reference definitions and click Create connector.
  7. To test the connector, you will need to create a new connection. Click Test, click New Connection under Connections, and click Create.
  8. Navigate back to the connector from the Custom connectors menu and click Test. From here, you can test the available operations.

Connect the Data Source to a PowerApp

Follow the steps below to connect to Wasabi from a PowerApp:

  1. From the PowerApps main menu, click Create an app and select the on-premises or cloud PowerApp Studio.
  2. Select a blank app (choose Phone layout or Tablet layout).
  3. In the View tab, click Data Sources and click Add data source.
  4. Click the Connection you created to test the connector.

Populate a Gallery

Follow the steps below to create a simple app that can search Wasabi data. You will use PowerApps formulas to bind Wasabi rows to rows in a gallery control.

  1. In the View tab, click Gallery -> Vertical to add a Gallery.

  2. After selecting a gallery, assign the Items property of the gallery to Wasabi data on the Advanced tab of the gallery settings. The formula below will allow you to access columns in the Buckets table.

    ForAll(CDataSwaggerAPI.getAllBuckets().value, {myName: Name, myOwnerId: OwnerId})
  3. Assign Wasabi columns to UI elements by clicking the element and then setting the Text property (on the Advanced tab of the UI element) to ThisItem.myName or ThisItem.myOwnerId.

Search Wasabi Data

To filter the records displayed by the gallery, add a TextInput to your Screen, clear the Text property for the TextInput, and set the Items property of the gallery to a formula like the one below, replacing TextInput1 with the name of the TextInput control in your gallery, if necessary:

If(IsBlank(TextInput1.Text), ForAll(CDataSwaggerAPI.getAllBuckets().value, {myName: Name, myOwnerId: OwnerId}), ForAll(CDataSwaggerAPI.getAllBuckets({'$filter':Concatenate("contains(Name,",TextInput1.Text,")")}).value, {myName: Name, myOwnerId: OwnerId}))

The formula builds an OData query that the API Server executes against the remote Wasabi data, ensuring that the search is run against the current data without first pulling in every record into the app. You can find more information on the supported OData in the API Server help documentation.