JeffreySu/WeiXinMPSDK · error · ArgumentException

文件名不能为空。

Error message

文件名不能为空。

What it means

ValidateImageFileName (ProductCouponApis.cs:809), used by UploadImageAsync, guards the WeChat product-coupon image upload API: the file name must be non-empty (and its extension must be jpg/png/jpeg etc.). An empty/whitespace fileName throws ArgumentException naming the parameter before any HTTP request is made.

Solutions

  1. Ensure a non-empty file path/name is passed to UploadImageAsync and check it before calling
  2. Verify the file exists and Path.GetFileName(path) yields a value with a supported extension (.jpg/.png/.jpeg)
  3. Add an upfront guard in your upload flow to reject empty file names with a friendly error

Example fix

// before
await api.UploadImageAsync(fileName); // fileName == ""

// after
if (string.IsNullOrWhiteSpace(fileName))
    throw new InvalidOperationException("Image file name must be provided");
await api.UploadImageAsync(fileName);
Defensive patterns

Strategy: validation

Validate before calling

if (string.IsNullOrWhiteSpace(fileName))
    throw new ArgumentException("Image file name is required", nameof(fileName));
var ext = Path.GetExtension(fileName)?.ToLowerInvariant();
if (ext is not (".jpg" or ".jpeg" or ".png"))
    throw new ArgumentException($"Unsupported image extension: {ext}");

Type guard

bool ValidImageName(string? fileName) =>
    !string.IsNullOrWhiteSpace(fileName) &&
    new[] { ".jpg", ".jpeg", ".png" }.Contains(Path.GetExtension(fileName)?.ToLowerInvariant());

Try / catch

try { await api.UploadImageAsync(fileName); }
catch (ArgumentException ex) when (ex.Message.Contains("文件名不能为空"))
{ logger.LogError(ex, "Empty file name passed to coupon image upload"); throw; }

Prevention

When it happens

Trigger: Calling UploadImageAsync with a null, empty, or whitespace-only fileName string, typically because the path variable was never assigned or an upload form field was missing.

Common situations: Reading a file name from user input/config that came back empty; passing Path.GetFileName on a path that had no filename; upload pipeline dropping the file name before reaching the API call.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of JeffreySu/WeiXinMPSDK@be573f6f94 (2026-09-12). Data as JSON: /api/errors/b7a3e32e3e8f9647. Report an issue: GitHub.

Appendix: source

Thrown at src/Senparc.Weixin.TenPay/Senparc.Weixin.TenPayV3/Apis/ProductCoupon/ProductCouponApis.cs:809

                              Escape(query[index + 1]));
                }
            }

            return parts.Count == 0
                ? path
                : $"{path}?{string.Join("&", parts)}";
        }

        private static string Escape(string value)
        {
            return Uri.EscapeDataString(value ?? string.Empty);
        }

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

            switch (Path.GetExtension(fileName)?.ToLowerInvariant())
            {
                case ".jpg":
                case ".jpeg":
                case ".bmp":
                case ".png":
                    return;
                default:
                    throw new ArgumentException(
                        "商品券图片仅支持 JPG、JPEG、BMP 或 PNG。",
                        nameof(fileName));
            }
        }
    }
}

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