前台代码: $("#douwn_a").click(function () {
                            $.get('@Url.Action("DownLoadFile", "Internet")?fileName=' + jsondata.routemsg[id - 1].filename + '&&filePath=' + jsondata.routemsg[id - 1].filepath + "&&" + new Date().getTime(), function (json) {

                            });
                        });

页面显示：
<a id="douwn_a" href="javascript:void(0)">下载</a></div>

后台代码: var newPath = this.Server.MapPath(filePath);

            //return File(newPath, "application/image/jpeg", fileName);
            if (!System.IO.File.Exists(newPath))
            {
                throw new ArgumentException("无效的文件名或文件不存在!");
            }

            return new BinaryContentResult()
            {
                FileName = fileName,
                ContentType = "application/image/jpeg",
                Content = System.IO.File.ReadAllBytes(newPath)
            };
 public class BinaryContentResult : ActionResult
        {
            public BinaryContentResult()
            {
            }

            // Properties for encapsulating http headers.
            public string ContentType { get; set; }
            public string FileName { get; set; }
            public byte[] Content { get; set; }

            // The code sets the http headers and outputs the file content.
            public override void ExecuteResult(ControllerContext context)
            {
                context.HttpContext.Response.ClearContent();
                context.HttpContext.Response.ContentType = ContentType;

                context.HttpContext.Response.AddHeader("content-disposition",
                    "attachment; filename=" + FileName);

                context.HttpContext.Response.BinaryWrite(Content);
                context.HttpContext.Response.End();
            }
        }