使用 MVC，您必须返回一个 ActionResult 才能响应。直接调整 http 响应不会利用 MVC 框架。
使用FileResult。在控制器内部，您有 File 处理此问题的方法。
memoryStream.Position = 0;
return File(memoryStream,
System.Net.Mime.MediaTypeNames.Application.Zip,
string.Format("Photos-{0:yyyyMMdd-HHmm}.zip", DateTime.Now));
但我怀疑错误出在您用于生成 zip 的代码中。尝试将ZipArchive 保存到磁盘进行检查。
否则，将ZipFileResult 类添加到您的项目并让它为您处理压缩。
这是我使用的类（使用 MVC 5）：
using System.IO.Compression;
using System.Web;
using System.Web.Mvc;
using System;
using System.Linq;
using System.IO;
using System.Net.Mime;
namespace Whatever
{
public class ZipFileResult : FileResult
{
/// <summary>
/// Folder inside zip which will contains the files.
/// (<c>FileDownloadName</c> without its extension will be used
/// by default if there is more than one file in the zip.
/// </summary>
/// <value>
/// <c>string.Empty</c> for not having a folder inside the zip.
/// <c>null</c> for using <c>FileDownloadName</c> without its extension
/// if there is more than one file in the zip.
/// </value>
/// <remarks>If <c>FileDownloadName</c> is <c>null</c> or empty, the
/// name "files" will be used instead.</remarks>
public string ZipFolder { get; set; }
private readonly ZipFileResultEntry[] _files;
public ZipFileResult(params ZipFileResultEntry[] files)
: base(MediaTypeNames.Application.Zip)
{
_files = files;
}
public ZipFileResult(params string[] filesPaths)
: this(filesPaths == null ? null :
filesPaths.Select(fp => ZipFileResultEntry
.Create(Path.GetFileName(fp), fp)).ToArray())
{
}
protected override void WriteFile(HttpResponseBase response)
{
// By default, response is fully buffered in memory and sent
// once completed. On big zipped content, this would cause troubles.
// If un-buffering response is required (<c>response.BufferOutput =
// false;</c>), beware, it may emit very small packets,
// causing download time to dramatically raise. To avoid this,
// it would then required to use a BufferedStream with a
// reasonnable buffer size (256kb for instance).
// http://stackoverflow.com/q/26010915/1178314
// The BufferedStream should encapsulate response.OutputStream.
// PositionWrapperStream must then Dispose it (current
// implementation will not), so long for this causing OutputStream
// to get closed (BufferedStream do not have any option for
// telling it not to close its underlying stream, and it is
// sealed...).
using (var outputStream =
new PositionWrapperStream(response.OutputStream))
using (var zip = new ZipArchive(outputStream,
ZipArchiveMode.Create, true))
{
if (_files != null)
{
var archiveDir = ZipFolder ??
(_files.Length <= 1 ? string.Empty :
string.IsNullOrEmpty(FileDownloadName) ?
"files" :
Path.ChangeExtension(FileDownloadName, null));
foreach (var file in _files)
{
if (file == null)
continue;
file.WriteEntry(zip, archiveDir);
}
}
}
}
// Workaround bug ZipArchive requiring Position while creating.
// Taken from http://stackoverflow.com/a/21513194/1178314
class PositionWrapperStream : Stream
{
private Stream _wrapped;
private int _pos = 0;
public PositionWrapperStream(Stream wrapped)
{
_wrapped = wrapped;
}
public override bool CanSeek { get { return false; } }
public override bool CanWrite { get { return true; } }
public override bool CanRead { get { return false; } }
public override long Position
{
get { return _pos; }
set { throw new NotSupportedException(); }
}
public override long Length { get { return _pos; } }
public override void Write(byte[] buffer, int offset, int count)
{
_pos += count;
_wrapped.Write(buffer, offset, count);
}
public override void Flush()
{
_wrapped.Flush();
}
protected override void Dispose(bool disposing)
{
// Fcd : not closing _wrapped ourselves, MVC handle that.
_wrapped = null;
base.Dispose(disposing);
}
// all the other required methods can throw NotSupportedException
public override int Read(byte[] buffer, int offset, int count)
{
throw new NotSupportedException();
}
public override void SetLength(long value)
{
throw new NotSupportedException();
}
public override long Seek(long offset, SeekOrigin origin)
{
throw new NotSupportedException();
}
}
}
public abstract class ZipFileResultEntry
{
/// <summary>
/// Filename to use inside the zip.
/// </summary>
public string Filename { get; private set; }
internal ZipFileResultEntry(string filename)
{
Filename = filename;
}
internal abstract void WriteEntry(ZipArchive zip, string directory);
/// <summary>
/// Create a file to zip in response from an uncompressed file.
/// </summary>
/// <param name="filename">Filename to use inside the zip.</param>
/// <param name="path">Full path to uncompressed file on
/// server.</param>
public static ZipFileResultEntry Create(string filename, string path)
{
return new FileSystemEntry(filename, path);
}
/// <summary>
/// Create a text file to zip in response using a callback.
/// </summary>
/// <param name="filename">Filename to use inside the zip.</param>
/// <param name="writer">Callback responsible of writing
/// uncompressed file content in zip stream.</param>
public static ZipFileResultEntry CreateText(string filename,
Action<StreamWriter> writer)
{
return new TextCallbackEntry(filename, writer);
}
private class FileSystemEntry : ZipFileResultEntry
{
private readonly string SystemPath;
public FileSystemEntry(string filename, string path)
: base(filename)
{
SystemPath = path;
}
internal override void WriteEntry(ZipArchive zip, string directory)
{
zip.CreateEntryFromFile(SystemPath,
Path.Combine(directory, Filename));
}
}
private class TextCallbackEntry : ZipFileResultEntry
{
private readonly Action<StreamWriter> Writer;
public TextCallbackEntry(string filename,
Action<StreamWriter> writer)
: base(filename)
{
if (writer == null)
throw new ArgumentNullException("writer");
Writer = writer;
}
internal override void WriteEntry(ZipArchive zip, string directory)
{
var entry = zip.CreateEntry(Path.Combine(directory, Filename));
using (var sw = new StreamWriter(entry.Open()))
{
Writer(sw);
}
}
}
}
}
然后您可以重写您的操作：
public ActionResult Download(List<int> photoIds)
{
var attachments = new List<string>();
foreach (int photoId in photoIds)
{
var Photo = db.Photos.Find(photoId);
attachments.Add(Server.MapPath(Photo.imageUrl));
}
return new ZipFileResult(attachments.ToArray())
{
FileDownloadName = string.Format("Photos-{0:yyyyMMdd-HHmm}.zip",
DateTime.Now)
};
}
旁注：出于性能原因，应避免在循环中调用 db。如果这是一个 EF 上下文，最好将其更改为（假设 Photo 具有 Id 属性作为主键）：
public ActionResult Download(int[] photoIds)
{
var attachments = new List<string>();
foreach (var photo in db.Photos.Where(p => photoIds.Contains(p.Id)))
{
attachments.Add(Server.MapPath(photo.imageUrl));
}
return new ZipFileResult(attachments.ToArray())
{
FileDownloadName = string.Format("Photos-{0:yyyyMMdd-HHmm}.zip",
DateTime.Now)
};
}