The DELETE statement conflicted with the SAME TABLE REFERENCE constraint

[HttpPost]
        [AllowUploadImagesOnly(".jpg,.gif,.png")]
        public virtual ActionResult ImageUpload(HttpPostedFileBase file)
        {
             var newFileName = Server.MapPath(Path.Combine(Links.SiteContents.Upload.Url(), file.FileName));
            file.SaveAs(newFileName);
            var array = new { filelink = newFileName };
            return Json(array, MediaTypeNames.Text.Plain, JsonRequestBehavior.AllowGet);
        }

[Required(ErrorMessageResourceType = typeof(ValidationErrorsResource),
            ErrorMessageResourceName = ResourceKeys.ValidationErrorsResource.RequiredField)]
        [MaxLength]
        [DisplayName("متن")]
        [AllowHtml]
        public string FullDescription { get; set; }

<div>متن: </div>
                <div>@Html.TextAreaFor(p => p.FullDescription)</div>
                <div>@Html.ValidationMessageFor(p => p.FullDescription)</div>

$('#FullDescription').redactor({
            autoformat: false,
            convertDivs: false
        });

@{
    var postUrl = Url.Action(actionName: "Delete", controllerName: "Student");
}
<div class="deleteDialog">
    <div>
        آیتم‌های انتخاب شده حذف خواهند شد. آیا تأیید می‌کنید؟
    </div>
    <p>
        <input type="submit" id="btn_SubmitDelete" value="حذف" />
        <input type="submit" id="btn_CancelDelete" value="انصراف" />
    </p>
</div>
<script type="text/javascript">
    $(function () {
        $("#btn_SubmitDelete").click(function (e) {
            var button = $(this);
            e.preventDefault();
            var data = "1,3,8,9";
            $.ajax({
                type: "POST",
                url: "@postUrl",
                data:  JSON.stringify({ ids: data}),
                contentType: "application/json; charset=utf-8",
                dataType: 'json',
                cache: false,
                beforeSend: function () { },
                success: function (html) {
                    alert(html);
                    $(".deleteDialog").parent("div").css("display", "none");
                },
                complete: function () {
                    button.removeAttr('disabled');
                    button.val("حذف");
                }
            });
        });
        $("#btn_CancelDelete").click(function (e) {
            e.preventDefault();
            var button = $(this);
            $(".deleteDialog").parent("div").css("display", "none");
        });
    });
</script>

[HttpGet]
 public ActionResult Delete()
 {
       return PartialView("Pv_Delete");
 }
 [HttpPost]
 [AjaxOnly]
  public ActionResult Delete(string ids)
  {
            var allIds = ids.Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries).ToList();
            Thread.Sleep(2000);
           if (true)
           {
                return Json(new { result = "ok" }, JsonRequestBehavior.AllowGet);
           }
            return Json(new { result = "error" });
 }