ServiceNow File content corrupted when calling Attachment API

Question

I'm calling the ServiceNow Attachment API to upload files but they are ending up corrupted even though they upload successfully.

ServiceNow Attachment API 
POST https://sn-host.com/api/now/attachment/file?table_name=YOURTABLE&table_sys_id=SYSID&file_name=FILENAME

A simple text file with content "test" is corrupted and the content looks like this:

-----------3056BD41-FD91-4B8C-8BCD-E35A47CAA7A3
Content-Disposition: form-data; name="file"; filename="b.txt"
Content-Type: application/x-gzip

test
-----------3056BD41-FD91-4B8C-8BCD-E35A47CAA7A3--

I'm using C# / RestSharp to call the upload api:

private static bool UploadFileBytes(byte[] file_bytes, string file_name, string table_name, string table_sys_id, string content_type)
{
    bool retval = false;
    try
    {
        string URL = SN_Srv_dest + $"/api/now/attachment/file?table_name={table_name}&table_sys_id={table_sys_id}&file_name={file_name}";
        Console.WriteLine("Post file to SN: " + URL);

        var client = new RestClient(URL);
        var request = new RestRequest(Method.POST);
        request.AddFileBytes("file", file_bytes, file_name);
        request.AddHeader("Content-Type", content_type);
        client.Authenticator = new HttpBasicAuthenticator(SN_Id_dest, SN_Pw_dest);
        IRestResponse response = client.Execute(request);
        if (response.IsSuccessful)
        {
            Console.WriteLine($"Post file {file_name} success: {response.Content}");
            retval = true;
        }
        else
        {
            Console.WriteLine($"Post file {file_name} failed: {response.Content}");
            retval = false;
        }
    }
    catch(Exception e)
    {
        Console.WriteLine($"Post file {file_name} failed: {e.Message}");
    }
    return retval;
}

Answer 1

I found the issue using the generated code in PostMan. The following line was causing the problem:

request.AddFileBytes("file", file_bytes, file_name);

I replaced it with this:

request.AddParameter("file", file_bytes, ParameterType.RequestBody);