c# - 如何在内存中构建ZipArchive并通过Web API 2中的IHttpActionResult下载？

Question

我有一个 Web API 2 ApiController使用以下 GET 方法:

[HttpGet]
public IHttpActionResult GetZip()
{
    return new ZipFileActionResult();
}

我的自定义实现 IHttpActionResult

public class ZipFileActionResult : IHttpActionResult
{
    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        var memoryStream = new MemoryStream();
        var response = new HttpResponseMessage(HttpStatusCode.OK);

        using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
        {
            var entry = archive.CreateEntry("MyFileName.txt");

            using (var streamWriter = new StreamWriter(entry.Open()))
            {
                streamWriter.Write("It was the best of times, it was the worst of times...");
            }

        }

        response.Content = new StreamContent(memoryStream);
        response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
        {
            FileName = "example.zip"
        };
        response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/zip");
        return Task.FromResult(response);
    }
}

当我使用 Postman 获取时，我收到“无响应”。断点，其中 StreamContent创建后显示流的长度约为 1000 字节。我错过了什么？

其他类似但不重复的问题

这个问题不是重复的，尽管它似乎有一些兄弟问题:

• ZipArchive creates invalid ZIP file但我没有保存到 Windows，所以我没有文件流。我还确保该流在 ZipArchive 之后保持打开状态已处置。
• Writing to ZipArchive using the HttpContext OutputStream但我并没有直接写信给 HttpContext.OutputStream ，当我流式传输到StreamContent时，我可以使用更简单的MemoryStream .

Answer 1

您必须将 memoryStream 位置重置为“0”，以便在写入响应时不会尝试从文件末尾开始。固定代码应如下所示:

using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
{
    var entry = archive.CreateEntry("MyFileName.txt");

    using (var streamWriter = new StreamWriter(entry.Open()))
    {
        streamWriter.Write("It was the best of times, it was the worst of times...");
    }
}

//ADD THIS LINE
memoryStream.Position = 0;    

response.Content = new StreamContent(memoryStream);