c# - 从 IFormFile 异常中获取内存流

Question

我上传了一张图片并想将它发送到第三方服务(Cloudinary)而不将文件保存在我的服务器中。

public async Task<List<string>> GetImagesUrlsByImage(IFormFile image)
{
    List<string> urlList = new List<string>();
    ImageUploadParams uploadParams = new ImageUploadParams();

    using (var memoryStream = new MemoryStream())
    {
        await image.CopyToAsync(memoryStream);
        uploadParams.File = new FileDescription(image.FileName, memoryStream);
        uploadParams.EagerTransforms = new List<Transformation>
        {
            new EagerTransformation().Width(200).Height(150).Crop("scale"),
            new EagerTransformation().Width(500).Height(200).Crop("scale")
        };

        ImageUploadResult result = await _cloudinary.UploadAsync(uploadParams);
        var url = result.SecureUrl.ToString();
        urlList.Add(url);
    }

    return urlList;
}

我没有得到异常，但来自 Cloudinary 的结果消息有一条错误消息:“无图像”；

调试时我看到这些错误:

我需要在此代码中修复什么？

Answer 1

最有可能的是，假设其他一切正常，您只需在 MemoryStream 中重置光标位置:

   ms.Position = 0;

如此完整的例子:

public async Task<List<string>> GetImagesUrlsByImage(IFormFile image)
{
    List<string> urlList = new List<string>();
    ImageUploadParams uploadParams = new ImageUploadParams();

    using (var memoryStream = new MemoryStream())
    {
        await image.CopyToAsync(memoryStream);

        ms.Position = 0; // set cursor to the beginning of the stream.

        uploadParams.File = new FileDescription(image.FileName, memoryStream);
        uploadParams.EagerTransforms = new List<Transformation>
        {
            new EagerTransformation().Width(200).Height(150).Crop("scale"),
            new EagerTransformation().Width(500).Height(200).Crop("scale")
        };

        ImageUploadResult result = await _cloudinary.UploadAsync(uploadParams);
        var url = result.SecureUrl.ToString();
        urlList.Add(url);
    }

    return urlList;
}