我在页面上有个file和button控件，然后调用ajax

  function upload() {
            var chk = true;
            $.ajax({
                url: "File.ashx",
                type: "POST",
                dataType: "json",
                contentType: "application/json; charset=utf-8 ;",
                async: false,
                success: function(data) {
                    if (data.d != 0) {
                        chk = false;
                        alert("失败");
                    }
                    else {
                        chk = true;
                        alert("成功");
                    }
                },
                error: function(x, s) {
                    alert("失败");
                }
            })
            return chk;
        }

这是我的ajax，但是我在File.ashx中context.Request.Files.Count没有数啊，

我的前台
      <input name="file" type="file" />
    <input id="Button1" type="button" value="button" onclick="return upload()" />

这是我的前台控件，有没有人指导下啊，谢谢了