思路是在后台将文件夹整体压缩为zip格式的压缩包，并返回文件流到前端，然后前端接收文件流实现浏览器下载的功能。

后端代码，将

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public async Task DownloadFiles(DownLoadModel input)
{
if (!Directory.Exists(input.pathUrl))
{
throw new UserFriendlyException(“当前要下载的文件夹不存在或已删除”);
}
var zipFileUrl = _configurationRoot[“downLoadUrlConf:downloadZipFileUrl”];
if (File.Exists(zipFileUrl))
{
File.Delete(zipFileUrl);
}
ZipHelper.CreateZip(input.pathUrl, zipFileUrl);
var memoryStream = new MemoryStream();
using (var stream = new FileStream(zipFileUrl, FileMode.Open))
{
await stream.CopyToAsync(memoryStream);
}
memoryStream.Seek(0, SeekOrigin.Begin);
return new FileStreamResult(memoryStream, “application/octet-stream”);//文件流方式，指定文件流对应的ContenType。
}
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public static class ZipHelper
{
///
/// 压缩文件
///
///
///
public static void CreateZip(string sourceFilePath, string destinationZipFilePath)
{
if (sourceFilePath[sourceFilePath.Length - 1] != System.IO.Path.DirectorySeparatorChar)
sourceFilePath += System.IO.Path.DirectorySeparatorChar;

        ZipOutputStream zipStream = new ZipOutputStream(File.Create(destinationZipFilePath));
        zipStream.SetLevel(6);  // 压缩级别 0-9
        CreateZipFiles(sourceFilePath, zipStream, sourceFilePath);

        zipStream.Finish();
        zipStream.Close();
    }
    /// <summary>
    /// 递归压缩文件
    /// </summary>
    /// <param name="sourceFilePath">待压缩的文件或文件夹路径</param>
    /// <param name="zipStream">
    /// <param name="staticFile"></param>
    private static void CreateZipFiles(string sourceFilePath, ZipOutputStream zipStream, string staticFile)
    {
        Crc32 crc = new Crc32();
        string[] filesArray = Directory.GetFileSystemEntries(sourceFilePath);
        foreach (string file in filesArray)
        {
            if (Directory.Exists(file))                     //如果当前是文件夹，递归
            {
                CreateZipFiles(file, zipStream, staticFile);
            }

            else                                            //如果是文件，开始压缩
            {
                FileStream fileStream = File.OpenRead(file);

                byte[] buffer = new byte[fileStream.Length];
                fileStream.Read(buffer, 0, buffer.Length);
                string tempFile = file.Substring(staticFile.LastIndexOf("\\") + 1);
                ZipEntry entry = new ZipEntry(tempFile);

                entry.DateTime = DateTime.Now;
                entry.Size = fileStream.Length;
                fileStream.Close();
                crc.Reset();
                crc.Update(buffer);
                entry.Crc = crc.Value;
                zipStream.PutNextEntry(entry);

                zipStream.Write(buffer, 0, buffer.Length);
            }
        }
    }
}

其中CreateZip方法传入一个源文件的路径，一个目标文件的路径，这里我的目标文件设置在appsetting.json里是个临时路径，只为前端当次下载使用。这样我们就在后台将数据以压缩包的形式压缩好，并返回数据流给前端了。

1.2 vue 下载压缩文件#
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<el-button
icon=“el-icon-download”
size=“mini”
type=“primary”
class=“pull-right”
@click=“downloadFile”
>下载文件到本地
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downloadFile() {
this.loading = true;
let postData = { pathUrl: this.filePathMag };
AjaxHelper.post(this.downLoadUrl, postData, {
responseType: “blob”,
}).then((res) => {
// 处理返回的文件流
const content = res.data;
const blob = new Blob([content], { type: “application/zip” });
const fileName = this.tenant.name + “配置信息.zip”;
if (“download” in document.createElement(“a”)) {
// 非IE下载
const elink = document.createElement(“a”);
elink.download = fileName;
elink.style.display = “none”;
elink.href = URL.createObjectURL(blob);
document.body.appendChild(elink);
elink.click();
URL.revokeObjectURL(elink.href); // 释放URL 对象
document.body.removeChild(elink);
} else {
// IE10+下载
navigator.msSaveBlob(blob, fileName);
}
this.loading = false;
});
},
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