“no_file_data” error when trying to upload file to slack

问题

when I try to upload any kidn of file through my SlackApp(via c# using HttpClient), I allways get the following response:

{"ok":false,"error":"no_file_data"}

I checked my ByteArray (I stream the file to an array and then try to upload) and wrote my data back into a .txt and .jpg - I tried both types of data. When i write them back they are exact copies from the original, so I guess my streaming and writing to an ByteArrayworks fine. But something is off with my upload.

I'll show you my code: The Client and the method to upload:

using System;
using System.Net.Http;
using System.Threading.Tasks;
using System.Net.Http.Headers;


namespace SlackApp
{
    public class SlackClient
    {
        private readonly Uri _webhookUrl;
        private readonly HttpClient _httpClient = new HttpClient {};

        public SlackClient(Uri webhookUrl)
        {
            _webhookUrl = webhookUrl;
        }

        public async Task<HttpResponseMessage> UploadFile(byte[] file)
        {
            var requestContent = new MultipartFormDataContent();
            var fileContent = new ByteArrayContent(file);
            fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");
            requestContent.Add(fileContent, "slack", "slack.txt");

            var response = await _httpClient.PostAsync(_webhookUrl, requestContent);
            return response;
        }
    }
}

the creation of the bytearray:

public class PostFile
{
    String path = @"C:\Users\f.held\Desktop\Held-Docs\dagged.jpg";

    public byte[] ReadImageFile()
    {            
        FileInfo fileInfo = new FileInfo(path);
        long imageFileLength = fileInfo.Length;
        FileStream fs = new FileStream(path, FileMode.Open, FileAccess.ReadWrite);
        BinaryReader br = new BinaryReader(fs);
        byte[] imageData = br.ReadBytes((int)imageFileLength);
        return imageData;
    }
}

the Main:

using System;
using System.Net.Http;
using System.Threading.Tasks;


namespace SlackApp
{
    class TestArea
    {
        public static void Main(string[] args)
        {    
            Task.WaitAll(IntegrateWithSlackAsync());
        }

        private static async Task IntegrateWithSlackAsync()
        {
            var webhookUrl = new Uri("https://slack.com/api/files.upload?token=xoxp-hereStandsMyToken&channel=MyChannel");  
            var slackClient = new SlackClient(webhookUrl);
            PostMessage PM = new PostMessage();
            PostFile PF = new PostFile();
            var testFile = PF.ReadImageFile();

            while (true)
            {
                var message = Console.ReadLine(); 
                FormUrlEncodedContent payload = PM.Content(message, "");
                var response = await slackClient.SendMessageAsync(payload);

                string content = await response.Content.ReadAsStringAsync();
                Console.WriteLine(content); //I build these two lines in here so I got the response from the method, and this is where it says "no_file_data"

                var isValid = response.IsSuccessStatusCode ? "valid" : "invalid";
                Console.WriteLine($"Received {isValid} response.");
                Console.WriteLine(response); //this puts out a "valid" response - oddly enough
            }
        }
    }
    }

Does anybody have an idea what is wrong here? Why isn't it taking the data?

回答1:

You have two bugs in your code:

main(): The parameter to specify the channels is called channels, not channel
UploadFile(): When you add your file content to the multipart you need to include the correct API parameter for the file which is file, not slack. And also want to include a reasonable filename (instead of slack.txt).

Additional comments

UploadFile(): Its wrong to set the content type to multipart/form-data. The correct type for that content would be image/jpeg. However, the correct type seams to be detected automatically, so just remove the line.
main(): The Slack API will always return OK (http 200, unless there is a network problem), so you want to also look on the ok and error properties of the JSON response instead.

Here is an update version of your code. I changed your main() method to include a call to `UploadFile()?.

using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;


namespace SlackApp
{
    public class PostFile
    {
        string path = @"C:\Users\Stratios_down.jpg";

        public byte[] ReadImageFile()
        {
            FileInfo fileInfo = new FileInfo(path);
            long imageFileLength = fileInfo.Length;
            FileStream fs = new FileStream(path, FileMode.Open, FileAccess.ReadWrite);
            BinaryReader br = new BinaryReader(fs);
            byte[] imageData = br.ReadBytes((int)imageFileLength);
            return imageData;
        }
    }

    public class SlackClient
    {
        private readonly Uri _webhookUrl;
        private readonly HttpClient _httpClient = new HttpClient { };

        public SlackClient(Uri webhookUrl)
        {
            _webhookUrl = webhookUrl;
        }

        public async Task<HttpResponseMessage> UploadFile(byte[] file)
        {
            var requestContent = new MultipartFormDataContent();
            var fileContent = new ByteArrayContent(file);            
            requestContent.Add(fileContent, "file", "stratios.jpg");

            var response = await _httpClient.PostAsync(_webhookUrl, requestContent);
            return response;
        }
    }

    class TestArea
    {
        public static void Main(string[] args)
        {
            Task.WaitAll(IntegrateWithSlackAsync());
        }

        private static async Task IntegrateWithSlackAsync()
        {
            var webhookUrl = new Uri(
                "https://slack.com/api/files.upload?token=xoxp-MY-TOKEN&channels=test"
            );
            var slackClient = new SlackClient(webhookUrl);

            PostFile PF = new PostFile();
            var testFile = PF.ReadImageFile();

            var response = await slackClient.UploadFile(testFile);

            string content = await response.Content.ReadAsStringAsync();
            Console.WriteLine(content);
            Console.ReadKey();

        }
    }
}

In addition I would have a couple of suggestions to improve your code.

Instead of including the additional API parameters in the URL, I would send them in the POST request as recommended by the API documentation.
Including the file as FileStream instead of loading it yourself into a ByteArray is the better approach and recommended for larger files.
Not sure why you need an infinite loop in your main. Those are really bad and should be avoided.

Please also take also a look at my new async example for uploading a file to Slack where I applied those two ideas.

来源：https://stackoverflow.com/questions/53283312/no-file-data-error-when-trying-to-upload-file-to-slack

标签

slack-api