Dynamic output file name of ApiHubFile Azure Function binding (one drive, drop box etc)

Question

I have an Azure Function with Timer Trigger, and then I want to generate a file with dynamic (defined in runtime) name and contents and save it to e.g. OneDrive.

My func

Answer 1

To have full control over the name and path of an output during function execution, you need to use imperative binding

For example: function.json

{
      "type": "blob",
      "name": "outputBinder",
      "path": "export/test",
      "connection": "AzureWebJobsStorage",
      "direction": "out"
},

Function:

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log, IBinder outputBinder)
{
     var attribute new BlobAttribute($"{some dynamic path}/{some dynamic filename}", FileAccess.Write);
     using (var stream = await outputBinder.BindAsync<Stream>(attribute))
     {
          // do whatever you want with this stream here...
     }
}

Answer 2

Here is how you could do it:

#r "Microsoft.Azure.WebJobs.Extensions.ApiHub"

using System;
using System.IO;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host.Bindings.Runtime;

public static async Task Run(TimerInfo myTimer, TraceWriter log, Binder binder)
{
    log.Info($"C# Timer trigger function executed at: {DateTime.Now}");    

    var fileName = "mypath/" + DateTime.Now.ToString("yyyy-MM-ddThh-mm-ss") + ".txt";

    var attributes = new Attribute[]
    {    
        new ApiHubFileAttribute("onedrive_ONEDRIVE", fileName, FileAccess.Write)
    };


    var writer = await binder.BindAsync<TextWriter>(attributes);
    var content = $"Generated at {DateTime.Now} by Azure Functions"; 

    writer.Write(content);
}

And the function.json file:

    {
  "bindings": [
    {
      "name": "myTimer",
      "type": "timerTrigger",
      "direction": "in",
      "schedule": "10 * * * * *"
    },
    {
      "type": "apiHubFile",
      "name": "outputFile",
      "connection": "onedrive_ONEDRIVE",
      "direction": "out"
    }
  ],
  "disabled": false
}

You shouldn't really need the apiHubFile declaration in your function.json but because of a bug I noticed today it should still be there. we will fix that bug.