JeffreySu/WeiXinMPSDK · error · InvalidDataException

上传文件超过允许上限 字节。

Error message

上传文件超过允许上限 {maxFileBytes.Value} 字节。

What it means

Before buffering the multipart upload, RequestMultipartCoreAsync checks whether the seekable fileStream's remaining length (Length - Position) exceeds the configured maxFileBytes and throws InvalidDataException if so. This is an early pre-flight size check so oversized uploads are rejected before any bytes are sent.

Solutions

1. Increase maxFileBytes to accommodate the actual file size (respecting WeChat Pay's per-media-type limits).
2. Validate fileStream.Length before calling and reject oversized files in your own UI/API with a friendly message.
3. If the stream was partially consumed, reset Position or pass a fresh stream so the remaining-length check measures the real content.
4. If the file is not required to be this large, compress or re-export the asset under the limit.

Example fix

// before
await apiRequest.RequestMultipartWithMaxSizeAsync(url, json, fs, maxFileBytes: 1_000_000);
// after
if (fs.Length - fs.Position <= 10 * 1024 * 1024)
{
    await apiRequest.RequestMultipartWithMaxSizeAsync(url, json, fs, maxFileBytes: 10 * 1024 * 1024);
}

if (fileStream.CanSeek && maxFileBytes.HasValue && fileStream.Length - fileStream.Position > maxFileBytes.Value)
    throw new InvalidOperationException($"File exceeds {maxFileBytes.Value} bytes limit.");

bool WithinLimit(Stream s, long? max) => !max.HasValue || !s.CanSeek || s.Length - s.Position <= max.Value;

try { /* multipart upload */ }
catch (InvalidDataException ex) { logger.LogWarning(ex, "Upload rejected: file too large"); return Results.PayloadTooLarge(); }

When it happens

Trigger: Calling any RequestMultipart* overload with a seekable FileStream whose remaining content is larger than maxFileBytes (e.g. a 12 MB certificate image when the limit is 10 MB).

Common situations: Uploading WeChat Pay media (brand images, certificates, complaint files) that grew past a hard-coded limit; limit configured too low for production files; users uploading large media through an app that forwards it to WeChat Pay.

Understand the failure class

Background: "File too large" / "file size exceeds limit" errors: why libraries cap file sizes and how to fix them — this error's family across 46 libraries.

Related errors

• 文件名不能为空。
• 方法路径不能为空
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• 单击按钮的key不能为空！
• 商家名片会员图片仅支持 JPG、JPEG、BMP 或 PNG。

AI-assisted analysis of JeffreySu/WeiXinMPSDK@be573f6f94 (2026-09-12). Data as JSON: /api/errors/cc3ceb3128177942. Report an issue: GitHub.

Appendix: source

Thrown at src/Senparc.Weixin.TenPay/Senparc.Weixin.TenPayV3/HttpHandlers/TenPayApiRequest.cs:394

            if (string.IsNullOrWhiteSpace(fileName))
            {
                throw new ArgumentException("文件名不能为空。", nameof(fileName));
            }

            _ = fileStream ?? throw new ArgumentNullException(nameof(fileStream));
            if (timeOut <= 0 && timeOut != Timeout.Infinite)
            {
                throw new ArgumentOutOfRangeException(nameof(timeOut), "超时时间必须大于 0，或使用 Timeout.Infinite。 ");
            }
            if (maxFileBytes.HasValue && maxFileBytes.Value <= 0)
            {
                throw new ArgumentOutOfRangeException(nameof(maxFileBytes),
                    "文件大小上限必须大于 0。");
            }
            if (maxFileBytes.HasValue && fileStream.CanSeek &&
                fileStream.Length - fileStream.Position > maxFileBytes.Value)
            {
                throw new InvalidDataException(
                    $"上传文件超过允许上限 {maxFileBytes.Value} 字节。");
            }

            T result = null;
            try
            {
                byte[] fileBytes;
                int fileLength;
                using (var memoryStream = new MemoryStream())
                {
                    var buffer = ArrayPool<byte>.Shared.Rent(81920);
                    try
                    {
                        int bytesRead;
                        while ((bytesRead = await fileStream.ReadAsync(buffer,
                            0, buffer.Length, cancellationToken)
                            .ConfigureAwait(false)) > 0)
                        {

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