ASP.NET MVC使用Session会话保持表单状态
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本篇实践在ASP.NET MVC 4下使用Session来保持表单的状态。
如上，输入俱乐部名称，点击"添加球员"，输入球员名称。我们希望，点击"到别的地方转转"跳转到另外一个视图页，当再次返回的时候能保持表单的状态。
点击"到别的地方转转"跳转到另外一个视图页如下：
再次返回，表单的状态被保持了：
点击"提交"按钮，显示表单的内容：
关于球员，对应的Model为：
using System.ComponentModel.DataAnnotations;
namespace MvcApplication1.Models
{
public class Player
{
public int Id { get; set; }
[Required(ErrorMessage = "必填")]
[Display(Name = "球员名称")]
public string Name { get; set; }
}
}关于俱乐部，对应的Model为：
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
namespace MvcApplication1.Models
{
public class Club
{
public Club()
{
this.Players = new List<Player>();
}
public int Id { get; set; }
[Required(ErrorMessage = "必填")]
[Display(Name = "俱乐部名称")]
public string Name { get; set; }
public List<Player> Players { get; set; }
}
}在Home/Index.cshtml强类型视图中，
@model MvcApplication1.Models.Club
@{
ViewBag.Title = "Index";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>Index</h2>
@using (Html.BeginForm("Index", "Home", FormMethod.Post, new {id = "myForm"}))
{
@Html.LabelFor(m => m.Name)
@Html.TextBoxFor(m => m.Name)
@Html.ValidationMessageFor(m => m.Name)
<br/><br/>
<ul id="players" style="list-style-type: none">
@if (Model.Players != null)
{
foreach (var item in Model.Players)
{
Html.RenderAction("NewPlayerRow", "Home", new { player = @item });
}
}
</ul>
<a id="addPlayer" href="javascript:void(0)" rel="external nofollow" rel="external nofollow" >添加球员</a>
<br/><br/>
<div>
<a href="javascript:void(0)" rel="external nofollow" rel="external nofollow" id="gotoOther">到别的地方转转</a>
<input type="submit" id="up" value="提交" />
</div>
}
@section scripts
{
<script src="~/Scripts/dynamicvalidation.js"></script>
<script type="text/javascript">
$(function () {
//添加关于Player的新行
$('#addPlayer').on("click", function() {
createPlayerRow();
});
//到别的页
$('#gotoOther').on("click", function() {
if ($('#myForm').valid()) {
$.ajax({
cache: false,
url: '@Url.Action("BeforeGoToMustSave", "Home")',
type: 'POST',
dataType: 'json',
data: $('#myForm').serialize(),
success: function (data) {
if (data.msg) {
window.location.href = '@Url.Action("RealGoTo", "Home")';
}
},
error: function (xhr, status) {
alert("添加失败，状态码：" + status);
}
});
}
});
});
//添加品牌行
function createPlayerRow() {
$.ajax({
cache: false,
url: '@Url.Action("NewPlayerRow", "Home")',
type: "GET",
data: {},
success: function (data) {
$('#players').append(data);
$.validator.unobtrusive.parseDynamicContent('#players li:last', "#myForm");
},
error: function (xhr, status) {
alert("添加行失败，状态码：" + status);
}
});
}
</script>
}以上，
点击"添加球员"，向控制器发出异步请求，把部分视图li动态加载到ul中
点击"到别的地方转转",向控制器发出异步请求，正是在这时候，在控制器的Action中，实施把表单的状态保存到Session中
点击"提交"按钮，把表单信息显示出来
另外，当在页面上点击"添加球员"，为了让动态的部分视图能被验证，需要引入dynamicvalidation.js，调用其$.validator.unobtrusive.parseDynamicContent('#players li:last', "#myForm")方法，dynamicvalidation.js具体如下：
//对动态生成内容客户端验证
(function ($) {
$.validator.unobtrusive.parseDynamicContent = function (selector, formSelector) {
$.validator.unobtrusive.parse(selector);
var form = $(formSelector);
var unobtrusiveValidation = form.data('unobtrusiveValidation');
var validator = form.validate();
$.each(unobtrusiveValidation.options.rules, function (elname, elrules) {
if (validator.settings.rules[elname] == undefined) {
var args = {};
$.extend(args, elrules);
args.messages = unobtrusiveValidation.options.messages[elname];
//edit:use quoted strings for the name selector
$("[name='" + elname + "']").rules("add", args);
} else {
$.each(elrules, function (rulename, data) {
if (validator.settings.rules[elname][rulename] == undefined) {
var args = {};
args[rulename] = data;
args.messages = unobtrusiveValidation.options.messages[elname][rulename];
//edit:use quoted strings for the name selector
$("[name='" + elname + "']").rules("add", args);
}
});
}
});
};
})(jQuery);在HomeController中，
public class HomeController : Controller
{
private const string sessionKey = "myFormKey";
public ActionResult Index()
{
Club club = null;
if (Session[sessionKey] != null)
{
club = (Club) Session[sessionKey];
}
else
{
club = new Club();
}
return View(club);
}
//提交表单
[HttpPost]
public ActionResult Index(Club club)
{
if (ModelState.IsValid)
{
StringBuilder sb = new StringBuilder();
sb.Append(club.Name);
if (club.Players != null && club.Players.Count > 0)
{
foreach (var item in club.Players)
{
sb.AppendFormat("--{0}", item.Name);
}
}
//删除Session
//Session.Abandon();
//Session.Clear();
Session.Remove(sessionKey);
return Content(sb.ToString());
}
else
{
return View(club);
}
}
//添加新行
public ActionResult NewPlayerRow(Player player)
{
return PartialView("_NewPlayer", player ?? new Player());
}
//跳转之前把表单保存到Session中
[HttpPost]
public ActionResult BeforeGoToMustSave(Club club)
{
Session[sessionKey] = club;
return Json(new { msg = true });
}
//保存完Club的Session后真正跳转到的页面
public ActionResult RealGoTo()
{
return View();
}
}以上，
对于接收[HttpGet]请求的Index方法对应的视图，Session存在就从Session中取出Club实例，否则就创建一个空的club实例
对于接收[HttpPost]请求的Index方法对应的视图，显示表单内容之前把对应的Session删除
添加新行NewPlayerRow方法供显示或添加用，当Player类型参数为null的时候，实际就是点击"添加球员"显示新行
BeforeGoToMustSave方法实际是为了在跳转之前保存Session
RealGoTo是点击"到别的地方转转"后真正跳转的视图页
另外，所有视图页的公共页Layout.cshtml，必须引用异步验证的js。
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width" />
<title>@ViewBag.Title</title>
@Styles.Render("~/Content/css")
@Scripts.Render("~/bundles/jquery")
@Scripts.Render("~/bundles/jqueryval")
</head>
<body>
@RenderBody()
@RenderSection("scripts", required: false)
</body>Home/_NewPlayer.cshtml部分视图，是在点击"添加球员"之后动态加载的部分视图。
@using MvcApplication1.Extension
@model MvcApplication1.Models.Player
<li class="newcarcolorli">
@using (Html.BeginCollectionItem("Players"))
{
@Html.HiddenFor(model => model.Id)
<div>
@Html.LabelFor(m => m.Name)
@Html.TextBoxFor(m => m.Name)
@Html.ValidationMessageFor(m => m.Name)
</div>
}
</li>其中，用到了扩展Extension文件夹下CollectionEditingHtmlExtensions类的扩展方法，如下：
using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Mvc;
namespace MvcApplication1.Extension
{
public static class CollectionEditingHtmlExtensions
{
//目标生成如下格式
//<input autocomplete="off" name="FavouriteMovies.Index" type="hidden" value="6d85a95b-1dee-4175-bfae-73fad6a3763b" />
//<label>Title</label>
//<input class="text-box single-line" name="FavouriteMovies[6d85a95b-1dee-4175-bfae-73fad6a3763b].Title" type="text" value="Movie 1" />
//<span class="field-validation-valid"></span>
public static IDisposable BeginCollectionItem<TModel>(this HtmlHelper<TModel> html, string collectionName)
{
//构建name="FavouriteMovies.Index"
string collectionIndexFieldName = string.Format("{0}.Index", collectionName);
//构建Guid字符串
string itemIndex = GetCollectionItemIndex(collectionIndexFieldName);
//构建带上集合属性+Guid字符串的前缀
string collectionItemName = string.Format("{0}[{1}]", collectionName, itemIndex);
TagBuilder indexField = new TagBuilder("input");
indexField.MergeAttributes(new Dictionary<string, string>()
{
{"name", string.Format("{0}.Index", collectionName)},
{"value", itemIndex},
{"type", "hidden"},
{"autocomplete", "off"}
});
html.ViewContext.Writer.WriteLine(indexField.ToString(TagRenderMode.SelfClosing));
return new CollectionItemNamePrefixScope(html.ViewData.TemplateInfo, collectionItemName);
}
private class CollectionItemNamePrefixScope : IDisposable
{
private readonly TemplateInfo _templateInfo;
private readonly string _previousPrfix;
//通过构造函数，先把TemplateInfo以及TemplateInfo.HtmlFieldPrefix赋值给私有字段变量，并把集合属性名称赋值给TemplateInfo.HtmlFieldPrefix
public CollectionItemNamePrefixScope(TemplateInfo templateInfo, string collectionItemName)
{
this._templateInfo = templateInfo;
this._previousPrfix = templateInfo.HtmlFieldPrefix;
templateInfo.HtmlFieldPrefix = collectionItemName;
}
public void Dispose()
{
_templateInfo.HtmlFieldPrefix = _previousPrfix;
}
}
/// <summary>
///
/// </summary>
/// <param name="collectionIndexFieldName">比如，FavouriteMovies.Index</param>
/// <returns>Guid字符串</returns>
private static string GetCollectionItemIndex(string collectionIndexFieldName)
{
Queue<string> previousIndices = (Queue<string>)HttpContext.Current.Items[collectionIndexFieldName];
if (previousIndices == null)
{
HttpContext.Current.Items[collectionIndexFieldName] = previousIndices = new Queue<string>();
string previousIndicesValues = HttpContext.Current.Request[collectionIndexFieldName];
if (!string.IsNullOrWhiteSpace(previousIndicesValues))
{
foreach (string index in previousIndicesValues.Split(','))
{
previousIndices.Enqueue(index);
}
}
}
return previousIndices.Count > 0 ? previousIndices.Dequeue() : Guid.NewGuid().ToString();
}
}
}Home/RealGoTo.cshtml视图，是点击"到别的地方转转"后跳转到的页面，仅仅提供了一个跳转到Home/Index视图页的链接。
@{
ViewBag.Title = "RealGoTo";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>RealGoTo</h2>
@Html.ActionLink("回到表单页","Index","Home")本篇的源码在这里：https://github.com/darrenji/KeepFormStateUsingSession
