<p>Form提交</p>

<form action="@Url.Action("SavePictureByForm")" enctype="multipart/form-data" method="post">

    <input id="pic" name="pic" type="file" />

    <input type="submit" value="提交" />

</form>

<p>Ajax.BeginForm</p>

@using(Ajax.BeginForm("SavePictureByForm", null, new AjaxOptions() { OnSuccess = "PostSuc", OnFailure = "PostFail", HttpMethod = "Post"}, new {enctype = "multipart/form-data"}))

{

   <input type="file" name="pic" id="pic" multiple="multiple" />

   <input type="submit" value="提交" />

}

 public ActionResult SavePictureByForm()

        {

            HttpFileCollectionBase files = Request.Files;

            var file = files[0];

            bool isOk = false;

            string msg = string.Empty;

            //....OtherDO

            return Content("<script>window.location.href='/home/index';</script>");

        }

<p>Ajax:以上传图片为例</p>

<input type="file" id="picAjax"/>

<input type="button" id="submitPic" value="提交" />

<img id="selImg"  src="" alt="用作图片预览" />

    var picString = "";

    $(function () {

        $("#picAjax").change(function (e) {

            var file = e.delegateTarget.files[0];

            //在此可以对选择的文件进行判断:文件类型 文件大小等

            //.....

            var reader = new FileReader();

            reader.readAsDataURL(file);

            reader.onload = function (ret) {

                picString = reader.result

                //预览图片

                $("#selImg").attr({ "src": picString });

            }

        });

        $("#submitPic").click(function () {

            $.ajax("home/SavePicture", {

                type: "post",

                datatype: "json",

                data: picString,

                error: function () { },

                success: function (result) {

                    if (result) {

                        alert(result.msg);

                    }

                }

            });

        });

 [HttpPost]

        public ActionResult SavePicture(string picString)

        {

            bool isOk = false;

            string msg = string.Empty;

            //其他操作

            //.........

            //.........

            return Json(new { suc = isOk, msg = msg });

        }