如何为RestSharp文件上传请求添加Content-Md5 Header解决AWS S3 BadDigest错误

我尝试将字符串列表以CSV格式上传至AWS S3的预签名URL，使用.NET默认HttpClient已成功实现，但使用RestSharp RestClient时失败，AWS返回错误：BadDigest - 您指定的Content-MD5与我们收到的不匹配。

输入参数说明：

• ids：字符串列表
• md5：通过System.Security.Cryptography库的md5.ComputeHash()计算得到的byte[]
• url：预签名URL

成功的HttpClient代码 #

using (var ms = new MemoryStream())
{
    using (var sw = new StreamWriter(ms, new UTF8Encoding(false), 8192, true))
    {
        sw.Write(string.Join(Environment.NewLine, ids));
    }
    ms.Position = 0;

    var file = ms.ToArray();
    var content = new ByteArrayContent(file);
    content.Headers.ContentType = new MediaTypeHeaderValue("text/csv");
    content.Headers.ContentLength = file.Length;
    content.Headers.ContentMD5 = md5;

    var client = new HttpClient();
    var result = client.PutAsync(url, content).Result;
    var response = result.Content.ReadAsString();
}

失败的RestSharp代码 #

using (var ms = new MemoryStream())
{
    using (var sw = new StreamWriter(ms, new UTF8Encoding(false), 8192, true))
    {
        sw.Write(string.Join(Environment.NewLine, ids));
    }
    ms.Position = 0;

    var file = ms.ToArray();
    var md5Based64 = Convert.ToBase64String(md5).Replace("-", "");
    var options = new FileParameterOptions
    {
        DisableFilenameEncoding = true,
    };
    var uploadRequest = new RestRequest()
        .AddFile("", file, "", "text/csv", options)
        .AddOrUpdateHeader("Content-Md5", md5Based64)
        .AddOrUpdateHeader("Content-Length", file.Length)
        .AddOrUpdateHeader("Content-Type", "text/csv");

    var restClient = new RestClient(
        new Uri(url), 
        configureSerialization: cfg =>
        {
            cfg.UseNewtonsoftJson();
        }, 
        useClientFactory: true
    );
    var response = restClient.ExecuteAsync(uploadRequest, Method.Put).Result;
}

修复建议及代码 #

问题根源 #

1. AddFile会将请求体包装为multipart/form-data格式，与你计算MD5的纯CSV内容不符
2. 多余的.Replace("-", "")操作破坏了正确的MD5 Base64值
3. 手动设置Content-Length和Content-Type会与RestSharp自动处理的内容冲突

修复后的代码 #

using (var ms = new MemoryStream())
{
    using (var sw = new StreamWriter(ms, new UTF8Encoding(false), 8192, true))
    {
        sw.Write(string.Join(Environment.NewLine, ids));
    }
    ms.Position = 0;

    var file = ms.ToArray();
    var md5Base64 = Convert.ToBase64String(md5); // 移除不必要的替换操作

    var uploadRequest = new RestRequest(Method.Put)
        .AddBody(file, "text/csv") // 直接上传纯字节数组，指定内容类型
        .AddOrUpdateHeader("Content-Md5", md5Base64); // 仅保留正确的MD5 Header

    var restClient = new RestClient(new Uri(url), configureSerialization: cfg =>
    {
        cfg.UseNewtonsoftJson();
    }, useClientFactory: true);

    var response = restClient.ExecuteAsync(uploadRequest).Result;
}

内容的提问来源于stack exchange，提问作者mdng