有一对夫妇在OP的代码错误。

There was a couple of mistakes in the OP's code.

通过提供的片段@马布，我发现对代码 http://www.briangrinstead.com/blog/multipart-form -post-在-C ，这里有一个的功能的*代码块附件上传至吉拉。

With the snippet provided by @mabu and the code I found on http://www.briangrinstead.com/blog/multipart-form-post-in-c, here's a functional* Code Block to Upload attachment to Jira.

public bool AddAttachments(string issueKey, IEnumerable<string> filePaths)
{
    string restUrl = Jira.FormatRestUrl(m_JiraId, true);
    string issueLinkUrl = String.Format("{0}/issue/{1}/attachments", restUrl, issueKey);

    var filesToUpload = new List<FileInfo>();
    foreach (var filePath in filePaths)
    {
        if (!File.Exists(filePath))
        {
            Jira.LogError("File '{0}' doesn't exist", filePath);
            return false;
        }

        var file = new FileInfo(filePath);
        if (file.Length > 10485760) // TODO Get Actual Limit
        {
            Jira.LogError("Attachment too large");
            return false;

        }

        filesToUpload.Add(file);
    }

    if (filesToUpload.Count <= 0)
    {
        Jira.LogWarning("No file to Upload");
        return false;
    }

    return PostMultiPart(issueLinkUrl, filesToUpload);
}

private Boolean PostMultiPart(string restUrl, IEnumerable<FileInfo> filePaths)
{
    HttpWebResponse response = null;
    HttpWebRequest request = null;

    try
    {
        var boundary = string.Format("----------{0:N}", Guid.NewGuid());
        var content = new MemoryStream();
        var writer = new StreamWriter(content);

        foreach (var filePath in filePaths)
        {
            var fs = new FileStream(filePath.FullName, FileMode.Open, FileAccess.Read);
            var data = new byte[fs.Length];
            fs.Read(data, 0, data.Length);
            fs.Close();

            writer.WriteLine("--{0}", boundary);
            writer.WriteLine("Content-Disposition: form-data; name=\"file\"; filename=\"{0}\"", filePath.Name);
            writer.WriteLine("Content-Type: application/octet-stream");
            writer.WriteLine();
            writer.Flush();

            content.Write(data, 0, data.Length);

            writer.WriteLine();
        }

        writer.WriteLine("--" + boundary + "--");
        writer.Flush();
        content.Seek(0, SeekOrigin.Begin);

        request = WebRequest.Create(restUrl) as HttpWebRequest;
        if (request == null)
        {
            Jira.LogError("Unable to create REST query: {0}", restUrl);
            return false;
        }

        request.Method = "POST";
        request.ContentType = string.Format("multipart/form-data; boundary={0}", boundary);
        request.Accept = "application/json";
        request.Headers.Add("Authorization", "Basic " + m_EncodedCredential);
        request.Headers.Add("X-Atlassian-Token", "nocheck");
        request.ContentLength = content.Length;

        using (Stream requestStream = request.GetRequestStream())
        {
            content.WriteTo(requestStream);
            requestStream.Close();
        }

        using (response = request.GetResponse() as HttpWebResponse)
        {
            if (response.StatusCode != HttpStatusCode.OK)
            {
                var reader = new StreamReader(response.GetResponseStream());
                Jira.LogError("The server returned '{0}'\n{1}", response.StatusCode, reader.ReadToEnd());
                return false;
            }

            return true;
        }
    }
    catch (WebException wex)
    {
        if (wex.Response != null)
        {
            using (var errorResponse = (HttpWebResponse)wex.Response)
            {
                var reader = new StreamReader(errorResponse.GetResponseStream());
                Jira.LogError("The server returned '{0}'\n{1}).", errorResponse.StatusCode, reader.ReadToEnd());
            }
        }

        if (request != null)
        {
            request.Abort();
        }

        return false;
    }
    finally
    {
        if (response != null)
        {
            response.Close();
        }
    }
}