Bing images for windows with Azure Logic Apps and Function Apps

These run in Azure and can be used to create workflows. A Logic App contains a workflow that consists of steps and conditions. Everything is based on calling API’s and weaving them together into a workflow. A step could be something like: Upload a file to OneDrive, which uses the OneDrive API.

Logic Apps connects to many API’s out of the box, like: GitHub, OneDrive, Azure Storage (Blob, Table), DropBox, Facebook, Google Drive, Instagram, CRM and so on. You can also write your own API’s and use them with Logic Apps. And last but not least, you can use Function Apps in Logic Apps.

These are sometimes called Azure Functions as well and that is confusing. Here is how I see it: a Function App is an app just like a Web App. A Fuction App can contain one or more Azure Functions.

You can use Function Apps to execute small pieces of code that optionally have input and output parameters. An example of a Function App is a small piece of code that is triggered every time a new blob is uploaded to Azure Blob Storage and that resizes the image and puts it back into Blob Storage. Its similar to what Azure WebJobs do, only now your code is independant from anything else; you don’t have to have a Web App or something else to use as a “server to run” in. Function Apps are an evolution of Azure WebJobs.

http://www.bing.com/HPImageArchive.aspx?format=xml&n=1&mkt=en-US

You can play with it by tweaking the query string:

* format

    * You can use xml, js for JSON or rss for RSS

* n=1

    * This tells the API how many images you want. n=5 returns 5 images. I think this is restricted to a maximum of 8 images

* mkt

    * This is your region. For instance en-US or nl-NL. I haven’t found that it produces different results, but people online seem to get different images in different regions

When you call the webservice, you get a result back like this:

   1: {

   2: images: [

   3: {

   4: startdate: "20160825",

   5: fullstartdate: "201608250700",

   6: enddate: "20160826",

   7: url: "/az/hprichbg/rb/GreatSandDunes_EN-US10806878209_1920x1080.jpg",

   8: urlbase: "/az/hprichbg/rb/GreatSandDunes_EN-US10806878209",

   9: copyright: "Great Sand Dunes National Park and Preserve, Colorado (© Ian Shive/Tandem Stills + Motion)",

  10: copyrightlink: "http://www.bing.com/search?q=Great+Sand+Dunes+National+Park+and+Preserve+Bing+road+trip&form=hpcapt&filters=HpDate:%2220160825_0700%22",

  11: wp: true,

  12: hsh: "95a15b330b2c60393b8f8581fec4343d",

  13: drk: 1,

  14: top: 1,

  15: bot: 1,

  16: hs: [ ]

  17: }

  18: ],

On line 7 you can see the URL to the image that you want. You can alter this URL to reflect the image size that you need, currently, this URL returns an image with a resolution of 1920x1080.

To be able to make a function App work in Logic Apps, for now your Function Apps have to be of the type Generic Webhook or HttpTrigger.

I wrote this piece of code for the Function App in the file run.csx:

   1: using System;

   2: using System.Net;

   3: using System.Net.Http;

   4: using System.Threading.Tasks;

   5: using Newtonsoft.Json.Linq;

   6: using System.Text;

   7:  

   8:  

   9: public static async Task<HttpResponseMessage> Run(HttpRequestMessage req)

  10: {

  11:     

  12: string url = await GetBingImageUrlAsync();

  13:  

  14:  

  15: HttpResponseMessage res = null;

  16:  

  17: res = new HttpResponseMessage(HttpStatusCode.OK)

  18: {

  19: //Content = new StringContent(url)

  20: Content = new StringContent(url)

  21: };

  22:  

  23: return res;

  24: }

  25:  

  26: static async Task<string> GetBingImageUrlAsync()

  27: {

  28: //use the HTTPclient, so that it is disposed after usage

  29: using (HttpClient client = new HttpClient())

  30: {

  31: //same goes for the HTTPresponse, make sure resources are cleaned after usage

  32: using (HttpResponseMessage response = await client.GetAsync("http://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=1&mkt=nl-NL"))

  33: {

  34: //and even the content is IDisposable, so use a using

  35: using (HttpContent content = response.Content)

  36: {

  37: //read the string from the response   

  38: string result = await content.ReadAsStringAsync();

  39:  

  40: //parse it using JSON.NET in a dynamic as we don't know exactly what is coming back

  41: dynamic jsonresult = JValue.Parse(result);

  42:                 

  43: return "http://www.bing.com/" + jsonresult.images[0].url;                       

  44:  

  45: }

  46: }

  47: }

  48: }

This does the following:

* It uses HttpClient to call the Bing URL for the JSON format (line 32)

* It reads the response content as a string (line 38)

* Next, it parses the JSON in the string result to a dynamic object using JValue, which is part of the Newtonsoft.Json library (line 41)

    * This creates an object that you can navigate through as you would the JSON tree. I use the dynamic object, because I don’t know for sure what the format of the reponse is

* Return the URL of the image as string (line 43)

* Wrap the URL up in a HttpResponse message and return it (line 20)

Function Apps can use libraries from NuGet. In this example, I use the Newtonsoft.Json package. You can import NuGet projects into your Function by adding a project.json file to the Function. Mine looks like this:

   1: {

   2: "frameworks": {

   3: "net46":{

   4: "dependencies": {

   5: "Newtonsoft.Json": "9.0.1"

   6: }

   7: }

   8: }

   9: }

You can create and manage Logic Apps in the Azure Portal. Mine looks like this:

 It does the following:

1. Run every 24 hour. The timer Trigger takes care of that

2. Call the Function App

3. Write the result, based on the output of the Function App

Lets look at how to call the Function App from the Logic App.

When you add a new step to a logic app, you can choose from a number of Connectors from different categories, including from Azure Functions in the same region:

Next, you can choose which Function App you want to select:

Notice that Logic Apps also keeps to the terminology of Function Apps and Functions.

We do not use any input parameters in our Function, but we do have to specify empty brackets { } to make it work.

This is because the Function will try to read the input as a JSON string and can’t seem to do that if nothing is passed, surely this will be solved in the future.