PHP Curl转.NET HttpRequest：多CSV文件带Token上传问题

Let's tackle this problem head-on. You're trying to convert a PHP cURL script for token-authenticated CSV uploads to C#, but ran into issues with WebClient's redirect loop and aren't sure if your RestClient implementation is correct. Here's how to fix everything:

First, let's confirm your token is being passed the same way as the PHP script. Assuming your PHP code looks like this (standard for token auth):

$ch = curl_init();
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "Authorization: Bearer YOUR_TOKEN_HERE"
]);
// ... rest of upload logic

Your C# code must mirror this header exactly. If the PHP script uses a custom header (e.g., X-Auth-Token), adjust your C# headers to match—this is critical for authentication to work.

The "Too many automatic redirections were attempted" error usually happens because:

• The server is sending a circular redirect (e.g., HTTP → HTTPS → HTTP repeatedly)
• WebClient's default redirect limit is hit (it's lower than you might expect)

Quick Fixes for WebClient: #

1. Disable auto-redirect and handle manually:

   webClient.AllowAutoRedirect = false;
   

   Then catch WebException and check for 3xx status codes to follow the redirect URL manually.
2. Use the correct protocol: Double-check if your upload URL should use https:// instead of http://—many servers force HTTPS and redirect repeatedly if you use HTTP.
3. Switch to HttpClient: WebClient is legacy; HttpClient has better redirect handling and is the recommended approach for .NET now.

Let's walk through the recommended HttpClient approach, plus a valid RestClient implementation, and a fixed WebClient version.

Recommended: HttpClient (.NET Core/.NET 5+) #

This is the modern, maintainable way to handle HTTP requests in .NET:

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

class CsvUploader
{
    static async Task Main(string[] args)
    {
        var authToken = "YOUR_AUTH_TOKEN";
        var uploadEndpoint = "https://your-server.com/upload";

        // Reuse HttpClient (don't create a new instance every time!)
        using var httpClient = new HttpClient();
        
        // Add token header to match PHP script
        httpClient.DefaultRequestHeaders.Authorization = 
            new AuthenticationHeaderValue("Bearer", authToken);

        // Build multipart form data (matches cURL's POSTFIELDS)
        using var formContent = new MultipartFormDataContent();

        // Add single CSV file
        var firstCsvPath = @"C:\data\file1.csv";
        var firstCsvBytes = await System.IO.File.ReadAllBytesAsync(firstCsvPath);
        var firstCsvContent = new ByteArrayContent(firstCsvBytes);
        firstCsvContent.Headers.ContentType = MediaTypeHeaderValue.Parse("text/csv");
        formContent.Add(firstCsvContent, "files", "file1.csv"); // "files" = form field name (match PHP!)

        // Add multiple CSV files (reuse the same field name)
        var secondCsvPath = @"C:\data\file2.csv";
        var secondCsvBytes = await System.IO.File.ReadAllBytesAsync(secondCsvPath);
        var secondCsvContent = new ByteArrayContent(secondCsvBytes);
        secondCsvContent.Headers.ContentType = MediaTypeHeaderValue.Parse("text/csv");
        formContent.Add(secondCsvContent, "files", "file2.csv");

        try
        {
            var response = await httpClient.PostAsync(uploadEndpoint, formContent);
            response.EnsureSuccessStatusCode(); // Throws if status code is 4xx/5xx

            var responseBody = await response.Content.ReadAsStringAsync();
            Console.WriteLine($"Upload succeeded! Response: {responseBody}");
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine($"Upload failed: {ex.Message}");
        }
    }
}

Valid RestClient (RestSharp) #

If you prefer RestSharp, make sure you're adding the token header and files correctly:

using RestSharp;
using System;

class RestSharpCsvUploader
{
    static void Main(string[] args)
    {
        var authToken = "YOUR_AUTH_TOKEN";
        var uploadEndpoint = "https://your-server.com/upload";

        var client = new RestClient(uploadEndpoint);
        var request = new RestRequest(Method.POST);

        // Add token header (match PHP!)
        request.AddHeader("Authorization", $"Bearer {authToken}");

        // Add single/multiple files
        request.AddFile("files", @"C:\data\file1.csv", "text/csv");
        request.AddFile("files", @"C:\data\file2.csv", "text/csv");

        try
        {
            var response = client.Execute(request);
            if (response.IsSuccessful)
            {
                Console.WriteLine($"Upload succeeded! Response: {response.Content}");
            }
            else
            {
                Console.WriteLine($"Upload failed. Status: {response.StatusCode}, Error: {response.ErrorMessage}");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Upload failed: {ex.Message}");
        }
    }
}

Fixed WebClient Implementation #

If you must use WebClient, here's how to handle multi-file uploads and fix redirects:

using System;
using System.Net;
using System.Text;

class WebClientCsvUploader
{
    static void Main(string[] args)
    {
        var authToken = "YOUR_AUTH_TOKEN";
        var uploadEndpoint = "https://your-server.com/upload";

        using var webClient = new WebClient();
        
        // Add token header
        webClient.Headers.Add("Authorization", $"Bearer {authToken}");
        
        // Fix redirect loop: disable auto-redirect (handle manually if needed)
        webClient.AllowAutoRedirect = false;

        try
        {
            var boundary = $"---------------------------{DateTime.Now.Ticks:x}";
            webClient.Headers.Add("Content-Type", $"multipart/form-data; boundary={boundary}");

            // Build multipart form data for multiple files
            var formBuilder = new StringBuilder();
            var filePaths = new[] { @"C:\data\file1.csv", @"C:\data\file2.csv" };
            
            foreach (var filePath in filePaths)
            {
                var fileName = System.IO.Path.GetFileName(filePath);
                formBuilder.AppendLine($"--{boundary}");
                formBuilder.AppendLine($"Content-Disposition: form-data; name=\"files\"; filename=\"{fileName}\"");
                formBuilder.AppendLine("Content-Type: text/csv");
                formBuilder.AppendLine();
                formBuilder.AppendLine(System.IO.File.ReadAllText(filePath));
            }
            formBuilder.AppendLine($"--{boundary}--");

            var responseBytes = webClient.UploadData(uploadEndpoint, "POST", Encoding.UTF8.GetBytes(formBuilder.ToString()));
            var response = Encoding.UTF8.GetString(responseBytes);
            Console.WriteLine($"Upload succeeded! Response: {response}");
        }
        catch (WebException ex)
        {
            Console.WriteLine($"Upload failed: {ex.Message}");
            if (ex.Response is HttpWebResponse response)
            {
                Console.WriteLine($"Status Code: {response.StatusCode}");
                // Handle redirect manually if needed
                if (response.StatusCode is HttpStatusCode.Redirect or HttpStatusCode.MovedPermanently)
                {
                    var newUrl = response.Headers["Location"];
                    Console.WriteLine($"Redirecting to: {newUrl}");
                    // Repeat upload logic for newUrl here
                }
            }
        }
    }
}

• Header Match: Confirm your C# token header is identical to the PHP script (e.g., Authorization: Bearer XYZ vs custom headers like X-Auth-Token).
• Form Field Name: The field name used for files (e.g., "files") must match what the server expects—this is set in the PHP CURLFile key.
• Protocol: Use https:// if your server enforces it to avoid unnecessary redirects.

内容的提问来源于stack exchange，提问作者user5407401