<script src="@Url.Content("~/Scripts/jquery-1.5.1.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.js")" type= "text/javascript "></script>

@{
    AjaxOptions ajaxOpt = new AjaxOptions { UpdateTargetId = "password" };
}

<div id="password">
    @using (Ajax.BeginForm("partPwd", ajaxOpt)) 
    ....

        [HttpPost]
        public ActionResult partPwd(FlatPartPwdModel flatPartPwdModel)
        {
            if (ModelState.IsValid)
            {
                int flatNum = int.Parse(this.User.Identity.Name);
                TempData["message"] = flatRepository.SaveFlat(flatNum, flatPartPwdModel.PasswordNew, flatPartPwdModel.PasswordConfirm, null);
            }
            if (Request.IsAjaxRequest())
                return PartialView();
            else
                return Redirect(Url.Action("Index"));
        }

@model TSJ.WebUI.Models.FlatPartPwdModel

<h3>Изменить пароль:</h3>

@Html.ValidationSummary(true)
@if (TempData["message"] != null)
    {<div class="Message">@TempData["message"]</div>}
@Html.EditorFor(m => m.PasswordNew)


@Html.EditorFor(m => m.PasswordConfirm)

@using (Ajax.BeginForm("partPwd", new AjaxOptions { UpdateTargetId = "password" })) 
{
    <div id="password">
        @Html.Action("partPwd")
    </div>
    <p><input type="submit" value="Изменить"/></p>
}

<script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.js")" type= "text/javascript "></script>

@Html.ValidationSummary()