Post message with file attached on slack

Question

I'm coding a simple console application in C# to communicate with Slack.com. I'm doing this via their WebApi. Currently I know how to post messages (with attachments, colored, links, users etc.) and send files to server.

If you send a file in a normal way ("Upload a file" on the left side of typing textbox) this file will be shown in the main conversation window. But how can you achieve the same thing via WebAPI ? Currently after sending the file, I can see it in the right side panel where all files are listed only.

Also there is a second question: is it possible to change to color of text in the message (no the "line" in attachment)?

This is the response after sending the file via https://slack.com/api/files.upload

{
    "ok": true,
    "file": {
        "id": "F04EX4***",
        "created": 1429279966,
        "timestamp": 1429279966,
        "name": "Testing.txt",
        "title": "Testing",
        "mimetype": "text\/plain",
        "filetype": "text",
        "pretty_type": "Plain Text",
        "user": "U*********",
        "editable": true,
        "size": 28,
        "mode": "snippet",
        "is_external": false,
        "external_type": "",
        "is_public": false,
        "public_url_shared": false,
        "url": "https:\/\/slack-files.com\/files-pub\/T*******\
/testing.txt",
        "url_download": "https:\/\/slack-files.com\/files-pub\/T************\
/download\/testing.txt",
        "url_private": "https:\/\/files.slack.com\/files-pri\/T*******\
/testing.txt",
        "url_private_download": "https:\/\/files.slack.com\/files-pri\/T**********\
 /download\/testing.txt",
        "permalink": "https:\/\/******.slack.com\/files\/******\
/F0******\/testing.txt",
        "permalink_public": "https:\/\/slack-files.com\/********",
        "edit_link": "https:\/\/******.slack.com\/files\/****\/F******\/testing.txt\/edit",
        "preview": "This is a test file number2.",
        "preview_highlight": "<div class=\
"sssh-code\"><div class=\"sssh-line\"><pre>This is a test file number2.<\/pre><\/div>\n
<\/div>",
        "lines": 1,
        "lines_more": 0,
        "channels": [],
        "groups": [],
        "ims": [],
        "comments_count": 0
    }
}

sorry, I don't know how to format this nicely.

The "is_external" and "is_public" are both false, maybe this is the reason - but how can I set them to "true" ?

->> Thank you for the edit! :) This is the whole function I'm using:

public static void SlackSendFile()
    {
        FileStream str = File.OpenRead(@"C:\Users\Eru\Desktop\Testing.txt");
        byte[] fBytes = new byte[str.Length];
        str.Read(fBytes, 0, fBytes.Length);
        str.Close();

        var webClient = new WebClient();
        string boundary = "------------------------" + DateTime.Now.Ticks.ToString("x");
        webClient.Headers.Add("Content-Type", "multipart/form-data; boundary=" + boundary);
        var fileData = webClient.Encoding.GetString(fBytes);
        var package = string.Format("--{0}\r\nContent-Disposition: form-data; name=\"file\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n{3}\r\n--{0}--\r\n", boundary, "Testing.txt", "multipart/form-data", fileData);

        var nfile = webClient.Encoding.GetBytes(package);
        string url = "https://slack.com/api/files.upload?token=" + Token + "&content=" + nfile + "&channels=[" + Channel + "]";

        byte[] resp = webClient.UploadData(url, "POST", nfile);

        var k = System.Text.Encoding.Default.GetString(resp);
        Console.WriteLine(k);
        Console.ReadKey();
    }

EDIT1: In this line:

 byte[] resp = webClient.UploadData(url, "POST", nfile);

The URL is:

 https://slack.com/api/files.upload?token=*********&content=System.Byte[]&channels=[%23*****]

Then I'm passing the byte array.

EDIT:

I have solved the problem. The thing was that the channel should be the ID of channel, not the name of the channel... stupid mistake :(

Answer 1

Hi here a clean example with RestSharp

public void UploadFile(string token, string filePath, string channel)
{
    var client = new RestClient("https://slack.com");

    var request = new RestRequest("api/files.upload", Method.POST);
    request.AddParameter("token", token);
    request.AddParameter("channels", channel);

    var fileInfo = new FileInfo(filePath);
    request.AddFile("file", File.ReadAllBytes(filePath), fileInfo.Name, contentType:"multipart/form-data");

    //Execute the request
    var response = client.Execute(request);
    var content = response.Content;
}

Answer 2

I had to change your code a little bit to get it working for anyone still looking for this. I needed to convert the file array to an ASCII encoded string, and then pulled the details into parameters.

    public static void SlackSendFile(string token, string channelId, string filepath)
    {
        FileStream str = File.OpenRead(filepath);
        byte[] fBytes = new byte[str.Length];
        str.Read(fBytes, 0, fBytes.Length);
        str.Close();

        var webClient = new WebClient();
        string boundary = "------------------------" + DateTime.Now.Ticks.ToString("x");
        webClient.Headers.Add("Content-Type", "multipart/form-data; boundary=" + boundary);
        var fileData = webClient.Encoding.GetString(fBytes);
        var package = string.Format("--{0}\r\nContent-Disposition: form-data; name=\"file\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n{3}\r\n--{0}--\r\n", boundary, "Testing.txt", "multipart/form-data", fileData);

        var nfile = webClient.Encoding.GetBytes(package);
        var encodedfile = System.Text.Encoding.ASCII.GetString(nfile);
        string url = "https://slack.com/api/files.upload?token=" + token + "&content=" + encodedfile + "&channels=" + channelId + "";

        byte[] resp = webClient.UploadData(url, "POST", nfile);

        var k = System.Text.Encoding.Default.GetString(resp);
        Console.WriteLine(k);
    }

Answer 3

If you add pretty=1 after channel property, it will work better.

Example:

string url = "https://slack.com/api/files.upload?token=" + token + "&content=" + nfile + "&channels=[" + Channel + "]&pretty=1"