Logic App Function App reading and writing Binary Files

Question

I am having a weird problem that I have been fighting with for several days. I have the Logic App below:

My Logic App is supposed to take Excel (template) as input from Sharepoint, write to it(using function app), and output a new Excel file to SFTP component. For simplicity to describe my problem, I am down to:

1. Read Excel file from Sharepoint
2. Put it through C# Function App that by the way takes it and is supposed to output the SAME FILE (so no Excel manipulation)
3. Write the output file to FTP.

When I run my function app locally and submit data using Postman, all looks good. I save function binary output and I can open it as Excel file. However, when I deploy my function app to Logic App, I can save output to FTP, but produced output file is not valid excel file. In Logic app SFTP component I am using "@binary(body('ConvertJsonToExcelV2'))"

What am I doing wrong? Please help! Here is my C# Function app code:

ConvertJsonToExcelV2.cs:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Attributes;
using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Enums;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;
using NwcDevFuncApps.ConvertJsonToExcelHelper;
using System.Net;
using System.Threading.Tasks;

namespace NwcDevFuncApps
{
    public static class ConvertJsonToExcelV2
    {
        [FunctionName("ConvertJsonToExcelV2")]
        [OpenApiOperation(operationId: "ConvertJsonToExcelRun", tags: new[] { "convertjsontoexcel" })]
        [OpenApiSecurity("function_key", SecuritySchemeType.ApiKey, Name = "code", In = OpenApiSecurityLocationType.Query)]
        [OpenApiRequestBody(contentType: "application/json", bodyType: typeof(string), Description = "The root object of the body is jsontoexcel. An Excel can be included in the body as a template or pre-data (jsontoexcel.prependdata.$content)")]
        [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "application/octet-stream", bodyType: typeof(object), Description = "The OK response")]
        public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req, ILogger log)
        {
            ConvertJsonToExcelWorkerV2 w = new ConvertJsonToExcelWorkerV2(req, log);
            IActionResult result = await w.DoWork();
            return result;
        }
    }
}

ConvertJsonToExcelWorkerV2.cs:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Runtime.ExceptionServices;
using System.Text;
using System.Threading.Tasks;

namespace NwcDevFuncApps.ConvertJsonToExcelHelper
{
    internal class ConvertJsonToExcelWorkerV2
    {
        private HttpRequest Req { get; set; } = null;
        private ILogger Log { get; set; } = null;

        public ConvertJsonToExcelWorkerV2(HttpRequest req, ILogger log)
        {
            Req = req;
            Log = log;
        }

        public async Task<IActionResult> DoWork()
        {
            FileContentResult res = null;
            JObject jsonData = null;

            string requestBody = new StreamReader(Req.Body).ReadToEnd();

            using (JsonTextReader reader = new JsonTextReader(new StringReader(requestBody)))
            {
                jsonData = (JObject)JToken.ReadFrom(reader);

                var prependJValue = (JValue)jsonData.SelectToken("jsontoexcel.prependdata.$content");
                var prependBase64String = prependJValue?.ToString();

                using (MemoryStream packageStream = new MemoryStream(Convert.FromBase64String(prependBase64String)))
                {
                    packageStream.Position = 0;

                    byte[] bytes = packageStream.ToArray();
                    res = new FileContentResult(bytes, "application/octet-stream");

                    packageStream.Close();
                }
                reader.Close();
            }
            return res;
        }
    }
}

Answer 1

1. Put it through C# Function App that by the way takes it and is supposed to output the SAME FILE (so no Excel manipulation)

If you are sending binary which is converted from base64 data, then you need to give something like this:

{
"$content-type":@{body('Get_file_content_using_path')['$content-type']},
"$content":@{outputs('Compose')['$content']}
}

then:

Output:

If binary is correctly formatted you will get output as i have got. I too agree with @Skin, that Logic apps is sufficient for many data operations.