C#后台如何接收前端JS发送的formdata对象

前端JS：

function fileUpload() {
    var formData = new FormData();
    formData.append("param1", "参数1");
    formData.append("param2", "参数2");
    formData.append("file1", $('#uploadfile1')[0].files[0]);
    $.ajax({
        url: 'Dosomething/Doit',//url
        type: 'post',
        data: formData,
        processData: false,
        contentType: false,
        async: false
    }).done(function (res) {
        ;
    }).fail(function (res) {
        ;
    });
}

后台接收：

[HttpPost]
public bool Doit()
{
    string p1=Request.Form["param1"]; //普通参数获取
    string p2=Request.Form["param2"];
    foreach(string upload in Request.Files.AllKeys)
    {
       HttpPostedFileBase file=Request.Files[uplooad];  //file可能为null
    }

      return true;
}