当debug到这里，你们就发现不管是 Request.Files["Upload"]亦或 Request.Files[0] 都不会取到文件流。
这就是我要说的，当使用Ajax.BeginForm(jquery.unobtrusive-ajax.js) 异步上传是不可行的，因为文件流不会被C#代码读取，但是并不影响 Ajax.BeginForm(jquery.unobtrusive-ajax.js) 异步提交表单的特性。
那我我们应该如何异步提交表单呢？
利用 $("#formID").ajaxSubmit({});这个方法异步提交表单并且上传文件。
第一步：引入js 注意顺序
<script src="/Style/js/jquery-1.8.3.min.js"></script><script src="~/Style/js/jquery-form.js"></script>
jquery-form.js下载地址：http://download.csdn.net/download/yusewuhen/7203209
第二步：
<form id="formID" method="post" enctype="multipart/form-data"> ???<div class="inner text-center"> ???????<table class="" id="mess"> ???????????<caption>基础信息</caption> ???????????<tr class="margin-top"> ???????????????<td class="padding-top text-center">手机号</td> ???????????????<td><input type="text" class="inputs" id="Phone" name="Phone"> </td> ???????????????<td><input type="button" value="获取验证码" id="sms" onclick="sendemail()"></td> ???????????</tr> ???????????<tr> ???????????????<td class="padding-top text-center">验证码</td> ???????????????<td><input type="text" class="inputs" id="Code" name="Code"></td> ???????????</tr> ???????????<tr> ???????????????<td class="padding-top text-center">身份证</td> ???????????????<td><input type="text" class="inputs" id="IdCard" name="IdCard"></td> ???????????</tr> ???????????<tr> ???????????????<td class="padding-top text-center">身份证照片</td> ???????????????<td> ???????????????????<div class="ge_pic_icon_Infor"> ???????????????????????<img src="images/zhengmian.png" /> ???????????????????</div> ???????????????????<div class="Infor_file"> ???????????????????????<input type="file" name="IdCardPos" id="IdCardPos" title="上传身份证正面照片" /> ???????????????????</div> ???????????????</td> ???????????????<td> ???????????????????<div class="ge_pic_icon_Infor2"> ???????????????????????<img src="images/fanmian.png" /> ???????????????????</div> ???????????????????<div class="Infor_file2"> ???????????????????????<input type="file" name="IdCardNeg" id="IdCardNeg" title="上传身份证反面照片" /> ???????????????????</div> ???????????????</td> ???????????</tr> ???????</table> ???????<input class="submit next-btn" type="button" value="下一步" onclick="next_step()" /> ???</div></form>
第三步：js处理异步提交
function next_step() { ???$("#formID").ajaxSubmit({ ???????url: "/College/BaseInfo", ????????type: "post", ???????success: function (data) { ???????????//alert("ok"); ???????????$(".detail-message6").css({ "display": "none" }); ???????????$(".detail-message7").css({ "display": "block" }); ???????}, ???????error: function (aa) { ???????????//console.log(aa); ???????????$(".detail-message2").css({ "display": "none" }); ???????????$(".detail-message6").css({ "display": "block" }); ???????????$(".detail-message7").css({ "display": "none" }); ???????} ???});}第四步：后台控制器处理
???????public ActionResult BaseInfo() ???????{ ???????????//上传的图片路径 ???????????string dir = "/Style/Upload/IdCard/"; ???????????HttpPostedFileBase IdCardPos = Request.Files["IdCardPos"]; ???????????HttpPostedFileBase IdCardNeg = Request.Files["IdCardNeg"]; ???????????#region 接收参数校验 ???????????if (string.IsNullOrWhiteSpace(Request["Phone"])) ???????????{ ???????????????return Content("手机号不能为空！"); ???????????} ???????????if (string.IsNullOrWhiteSpace(Request["Code"])) ???????????{ ???????????????return Content( "验证码不能为空！"); ???????????} ???????????if (string.IsNullOrWhiteSpace(Request["IdCard"])) ???????????{ ???????????????return Content( "身份证号不能为空！"); ???????????} ???????????if (IdCardPos == null) ???????????{ ???????????????return Content("请上传身份证正面照片！"); ???????????} ???????????if (IdCardNeg == null) ???????????{ ???????????????return Content("请上传身份证反面照片！"); ???????????} ???????????#endregion ???????????//获取缓存的验证码 ???????????Object Code = CacheOpt.GetCache("Code"); ???????????if (Code.ToString() != Request["Code"] || String.IsNullOrEmpty(Code.ToString())) ???????????{ ???????????????return Content("手机验证码不正确或已失效,请重新获取验证码！"); ???????????} ???????????#region 上传身份证照片 ???????????Dictionary<string, string> DicInfo = new Dictionary<string, string>(); ???????????Dictionary<string, string> DicInfo2 = new Dictionary<string, string>(); ???????????try ???????????{ ???????????????????????????????DicInfo = UploadImg(IdCardPos, dir); ???????????????if (DicInfo["Result"] == "0") ???????????????{ ???????????????????return Content("身份证正面照片上传的类型错误！"); ???????????????} ??????????????????????????????DicInfo2 = UploadImg(IdCardNeg, dir); ????????????????????????????????????????????????if (DicInfo2["Result"] == "0") ???????????????{ ???????????????????return Content("身份证反面照片上传的类型错误！"); ???????????????} ???????????} ???????????catch ???????????{ ???????????????return Content("身份证正照片上传失败！"); ???????????} ???????????#endregion ???????????#region 将数据提添加到集合中 ???????????Dictionary < string, string> myDic = new Dictionary<string, string>(); ???????????myDic.Add("Phone", Request["Phone"]); ???????????myDic.Add("IdCard", Request["IdCard"]); ???????????myDic.Add("IdCardPos", DicInfo["ImagePath"]); ???????????myDic.Add("IdCardNeg", DicInfo2["ImagePath"]); ???????????myDic.Add("Status", Convert.ToString("1")); ???????????#endregion ???????????#region 添加数据到数据库 ???????????????????????????bool res = collegeService.AddBaseInfo1(myDic); ???????????if (res == false) ???????????{ ???????????????return Content("fail"); ???????????} ???????????#endregion ???????????return Content("ok"); ???????} ???????#region 上传图片 ???????private Dictionary<string, string> UploadImg(HttpPostedFileBase file, string dir) ???????{ ???????????string Image_Path = null; ?????????//保存的文件 ???????????Dictionary<string, string> DicInfo = new Dictionary<string, string>(); ?//返回的文件信息 ????????????????//判断上传文件的类型 ???????????string fileName = Path.GetFileName(file.FileName); //获取文件名 ???????????string fileExt = Path.GetExtension(fileName); ?????//获取扩展名 ???????????if (fileExt == ".jpg" || fileExt == ".gif" || fileExt == ".png") ???????????{ ???????????????//创建文件夹 ???????????????Directory.CreateDirectory(Path.GetDirectoryName(Request.MapPath(dir))); ???????????????//需要对上传的文件进行重命名 ???????????????string newfileName = Guid.NewGuid().ToString(); ???????????????//构建文件完整路径 ???????????????string fullDir = dir + newfileName + fileExt; ???????????????file.SaveAs(Request.MapPath(fullDir)); ?//保存文件 ?????????????????//将上传成功的图片的路径存到数据库中 ???????????????Image_Path = newfileName + fileExt; ???????????????DicInfo.Add("ImagePath", Image_Path); ???????????????DicInfo.Add("Result","1"); ???????????} ???????????else ???????????{ ???????????????DicInfo.Add("ImagePath", ""); ???????????????DicInfo.Add("Result", "0"); ???????????} ???????????return DicInfo; ???????} ???????#endregion当debug到这里，你们就发现不管是 Request.Files["Upload"]亦或是 Request.Files[0] 都可以取到文件流。
当controller返回值也可以成功进入seccess方法中。
请注意我代码中标红的位置，以防遗漏导致一直debug无果问题！
总结一下：
1.MV5 5.0中异步提交表单方法两种：
Ajax.BeginForm(new AjaxOptions:post) 和 $("#formID").ajaxSubmit({})
2.MVC 5.0中异步提交表单上传文件一种：
$("#formID").ajaxSubmit({})
asp.net mvc Ajax.BeginForm 异步上传图片的问题
原文地址：http://www.cnblogs.com/zouke1220/p/7462713.html