How to pass a file to an API from Azure Logic App - api

Question

I have a simple Logic App. The trigger is on New file (ex: Dropbox, OneNote, etc.)
I want to pass the filename and the fileContent to a API APP (web Api).
But I got error, or worse the content is null once in the API!
The API is in C#.
How do you pass a file (ex: pdf, png) to and API from Logic App
UPDATE:
In Logic App here my action code:
"UploadNewFile": {
"inputs": {
"method": "post",
"queries": {
"filedata": {
"fileName":"#triggerOutputs()['headers']['x-ms-file-name']",
"fileContent":"#base64(triggerBody())"
}
},
"uri": "https://smartuseconnapiapp.azurewebsites.net/api/UploadNewFile"
},
"metadata": {
"apiDefinitionUrl": "https://smartuseconnapiapp.azurewebsites.net/swagger/docs/v1",
"swaggerSource": "website"
},
"runAfter": {},
"type": "Http"
}
In my API App, If the function is declared like this filedata is null
[Route("api/UploadNewFile")]
[HttpPost]
public HttpStatusCode UploadNewFile([FromBody] string filedata)
And if I don't add the [FromBody] like that I got an error.
[Route("api/UploadNewFile")]
[HttpPost]
public HttpStatusCode UploadNewFile(string filedata)

Answer 1

Yes you can send binary content to your own API in a few different methods. Our out-of-the-box actions use this as well.
If you want to send the binary contents as the request body
For example, an outgoing request from the Logic App could have binary content and a content-type header of image/png
In this case the swagger for the body of your request should be binary - or:
{ "name": "body",
"In": "body",
"Schema": {
"Type":"string",
"Format": "binary"
} ... }
That should tell the designer that the request body is binary content. If a previous action or the trigger had binary data (e.g. "When a file is added to FTP") and you used that output in the body, it would show up in your custom API inputs as:
"Body": "#triggerBody()"
Notice there are no { and } on the expression (string interpolations) which would convert the binary content to a string. This would send an outgoing request to the connector with the binary content - so your controller just needs to accept binary content and honor the content-type header as needed.
If you want to send binary content in a JSON request
Sometimes you don't want to send binary as the full request, but as a property of another object. For instance a person object may have a name, address, and profile pic all in the request body. In this case we recommend sending the binary content as base64 encdoded. You can use "format": "base64" in swagger to describe a property as this. In code-view would look something like:
"Body": {
"Name": "#triggerBody()['Name']",
"ProfilePic": "#base64(body('Dropbox'))"
}
Hope that helps. Let me know if you have any questions - here is an article on how logic apps preserves content-types as well.

Answer 2

I found how to to it.
I needed to pass the filename in the querystring and the file in the body of the HTTP Request. Today, it's not possible to do it using the design view so you need to go in code view.
In the Logic App code
"queries": {
"fileName": "#{triggerOutputs()['headers']['x-ms-file-name']}"
},
"body": "#triggerBody()"
In the API App code
public HttpResponseMessage UploadNewFile([FromUri] string fileName)
{
var filebytes = Request.Content.ReadAsByteArrayAsync();
[...]
}
A more detailed explanation can be found in this blog post:
http://www.frankysnotes.com/2017/03/passing-file-from-azure-logic-app-to.html