c# - 如何在内存中构建一个 ZipArchive 并通过 Web API 2 中的 IHttpActionResult 下载？

Question

我有一个具有以下 GET 方法的 Web API 2 ApiController:

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

我对 IHttpActionResult 的自定义实现

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，我得到“无响应”。创建 StreamContent 的断点显示流的长度约为 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，虽然它似乎有一些 sibling :

• ZipArchive creates invalid ZIP file但我没有保存到 Windows，所以我没有文件流。我还确保流在 ZipArchive 处理后保持打开状态。
• Writing to ZipArchive using the HttpContext OutputStream但我没有直接写到 HttpContext.OutputStream，因为我流式传输到 StreamContent，我可以使用更简单的 MemoryStream。<

Answer 1

您必须将 memoryStream 位置重置为“0”，这样它在写入响应时就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);