API controller not returning File after hosted on AWS lambda

Question

WE are running into an issue where a file is not getting downloaded correctly when hosted as an AWS lambda package.

.Net Core API GET Endpoint that returns

    [HttpGet()]
    [Route("ABC")]
    public async Task<IActionResult> ABC(string id)
    {  byte[] con = GetFileContent(id);
       var fileName = GetFileName(id);
       return File(con, "application/octet-stream", filename);     
    }

When we run this on local host (IISExpress) this return the file with content

But when the same is build into an AWS lambda package and deployed, it downloads the file but the file does not open and gives error as corrouted, etc

Do we need to set something in lambda to allow this download to work correctly?

Also, when we run this on POSTMan

on Local: it Returns the file in Response(Encoded- File with strange characters) On Dev: It returns the byte[]??

Norm Johanson · Accepted Answer · 2019-12-21 16:20:59Z

1

You need to go into the Amazon API Gateway console and enable binary responses. https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-payload-encodings-configure-with-console.html

What you are doing in the console is saying what Accept or content-types header values to look at on the request to determine if it is okay to return binary data. Since you can't really control the Accept header in the browser which I suspect you are calling from then setting a wildcard character in the console would probably be easiest.

answered Dec 21, 2019 at 16:20

Norm Johanson

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1 Comment

fireholster Over a year ago

Thanks for the reply. So a redeploy of API gateways for the lambda resolved the issue. We just found out that changes in response headers require Gateway refresh. We had new headers added as part of this new endpoint.

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