在 ASP.NET Core 1.0 上处理大文件上传

使用Microsoft.AspNetCore.WebUtilities.MultipartReader，因为它...

可以用最小的缓冲来解析任何流.它一次给你每个部分的标题和正文，然后你可以对该部分的正文做你想做的事情(缓冲、丢弃、写入磁盘等等).

下面是一个中间件示例.

app.Use(async (context, next) =>
{
    if (!IsMultipartContentType(context.Request.ContentType))
    {
        await next();
        return;
    }

    var boundary = GetBoundary(context.Request.ContentType);
    var reader = new MultipartReader(boundary, context.Request.Body);
    var section = await reader.ReadNextSectionAsync();

    while (section != null)
    {
        // process each image
        const int chunkSize = 1024;
        var buffer = new byte[chunkSize];
        var bytesRead = 0;
        var fileName = GetFileName(section.ContentDisposition);

        using (var stream = new FileStream(fileName, FileMode.Append))
        {
            do
            {
                bytesRead = await section.Body.ReadAsync(buffer, 0, buffer.Length);
                stream.Write(buffer, 0, bytesRead);

            } while (bytesRead > 0);
        }

        section = await reader.ReadNextSectionAsync();
    }

    context.Response.WriteAsync("Done.");
});

这是帮手.

private static bool IsMultipartContentType(string contentType)
{
    return 
        !string.IsNullOrEmpty(contentType) &&
        contentType.IndexOf("multipart/", StringComparison.OrdinalIgnoreCase) >= 0;
}

private static string GetBoundary(string contentType)
{
    var elements = contentType.Split(' ');
    var element = elements.Where(entry => entry.StartsWith("boundary=")).First();
    var boundary = element.Substring("boundary=".Length);
    // Remove quotes
    if (boundary.Length >= 2 && boundary[0] == '"' && 
        boundary[boundary.Length - 1] == '"')
    {
        boundary = boundary.Substring(1, boundary.Length - 2);
    }
    return boundary;
}

private string GetFileName(string contentDisposition)
{
    return contentDisposition
        .Split(';')
        .SingleOrDefault(part => part.Contains("filename"))
        .Split('=')
        .Last()
        .Trim('"');
}

外部参照

• https://github.com/aspnet/HttpAbstractions/pull/146个
• https://github.com/aspnet/HttpAbstractions个