1. 客户端

发送Get请求某个Action，将filePath作为查询参数传递
例如：

location.href='//www.greatytc.com/Content/DownloadFile?filePath='+filePath;

或者<a href="//www.greatytc.com/Content/DownloadFile?filePath=... ">fileName</a>

2. 服务器端

public ActionResult DownloadFile(string filePath)
{
    FileInfo info = new FileInfo(filePath);
    long fileSize = info.Length;

    Response.Clear();
    Response.ContentType = "application/x-zip-compressed";
    Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(Path.GetFileName(filePath)));
    Response.AddHeader("Content-Length", fileSize.ToString());
    Response.TransmitFile(filePath, 0, fileSize);
    Response.Flush();

    return null;
}

注：
在Response Header中加入的“filename=”，用来指定下载到客户端的默认文件名。