ViewData,ViewBag,TempData

ViewData和ViewBag是一回事，只能在当前View中有效

TempData里的值可以RedirectToAction跳转Controller或Action依然有效，等这次http请求结束后，TempData被清空

ViewBag和ViewData生命周期相同，仅对当前View有效，不同的是ViewBag的类型不再是字典的键值对结构，而是dynamic动态类型。

TempData在第一次读取之后会被移除.多用于跨control.

如果我们想读取TempData的值但是又不让它被删除，可以使用TempData.Peek("Key")方法。如果想再保持一次TempData里面的值，可以使用TempData.Keep("Key").

 ====1、TempData==============

ASP.NET MVC的TempData用于传输一些临时的数据，例如在各个控制器Action间传递临时的数据或者给View传递一些临时的数据，相信大家都看过“在 ASP.NET页面间传值的方法有哪几种”这个面试题，在ASP.NET MVC中TempData的就是其中的一种传值方法。TempData默认是使用Session来存储临时数据的，TempData中存放的数据只一次访 问中有效，一次访问完后就会删除了的。这个一次访问指的是一个请求到下一个请求，因为在下一个请求到来之后，会从Session中取出保存在里面的 TempData数据并赋值给TempData，然后将数据从Session中删除。我们看一下ASP.NET MVC Preview5源码：

image

也就是说TempData只保存到下一个请求中，下一个请求完了之后，TempData就会被删除了。注意这里TempData使用Session 来做存储的，Session是对应特定用户的，所以并不存在并发问题。如果你用数据库来做TempData的存储介质的话，必须要考虑这个情况的。至于如 何自定义TempData的存储介质，你可以参考“ASP.NET MVC: 用db4o来做TempDataProvider(另附一个泛型的RedirectToAction方法)”这一篇文章。

前面说到的在我们的BaseController中有一个显示提示信息给用户的方法，这个提示信息就是临时的信息，我们可以使用TempData来实现。下面让我们来实现这个提示信息的方法：

复制代码
protected ActionResult ShowMsg(List<string> msgs)
{
TempData["Messages"] = msgs;
return RedirectToAction("Message");
}

public ActionResult Message()
{
return View(TempData["Messages"] as List<string>);
}
复制代码

因为我们的Controller都继承自这个我们自定义的BaseController，所以我么可以才Controller中这样来给用户显示提示信息：

image

TEMPDATA应用例子，通过TEMPDATA实现添加数据时防止页面刷新出现重复提交数据的情况：

STEP01：保存数据到TEMPDATA，定义页面跳转到结果显示页

 public ActionResult Save(Models.GuestBookForm data)
        {

            if (!ModelState.IsValid)
            {
                //验证失败
                return RedirectToAction("Write");
            }

            MvcStudyDemo.Models.MvcGuestbookEntities db = new Models.MvcGuestbookEntities();

            db.AddToMessage(new Models.Message()
            {

                Body = data.MsgName + data.Email,
                AdminReply = data.Content,
                IsSecret = false,
                AdminReplyTime = DateTime.Now,
                CreateTime = DateTime.Now,
                MemberID = 38

            });

            db.SaveChanges();

            //ViewData["Name"] = data.MsgName;
            //ViewData["Email"] = data.Email;
            //ViewData["Content"] = data.Content;


            //return View();


            //保存临时数据，页面跳转防止重复提交
            TempData["LastPostGuestBookForm"] = data;

            return RedirectToAction("Result");


        }

STEP2：新建RESULT动作

 public ActionResult Result()
        {
            if (TempData["LastPostGuestBookForm"] == null)
            {
                return RedirectToAction("Index");
            }

            var model = (Models.GuestBookForm)TempData["LastPostGuestBookForm"];

            return View(model);
        }

STEP3：新建RESULT动作视图

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<MvcStudyDemo.Models.GuestBookForm>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
 Result
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>Result</h2>

    <fieldset>
        <legend>Fields</legend>
       
        <div class="display-label">MsgName</div>
        <div class="display-field"><%: Model.MsgName %></div>
       
        <div class="display-label">Email</div>
        <div class="display-field"><%: Model.Email %></div>
       
        <div class="display-label">Content</div>
        <div class="display-field"><%: Model.Content %></div>
       
    </fieldset>
    <p>
        <%: Html.ActionLink("Back to List", "Index") %>
    </p>

</asp:Content>

 二、ViewData与ViewBag

在Asp.net MVC 3 web应用程序中，我们会用到ViewData与ViewBag，对比一下： 
    
 
ViewData
 
ViewBag
 
它是Key/Value字典集合
 
它是dynamic类型对像
 
从Asp.net MVC 1 就有了
 
ASP.NET MVC3 才有
 
基于Asp.net 3.5 framework
 
基于Asp.net 4.0与.net framework
 
ViewData比ViewBag快
 
ViewBag比ViewData慢
 
在ViewPage中查询数据时需要转换合适的类型
 
在ViewPage中查询数据时不需要类型转换
 
有一些类型转换代码
 
可读性更好
 
   
在Controller中使用ViewData:
public ActionResult UsingViewData()
{
    
    ViewData["Title"] = " Using ViewData";
    ViewData["ProjectName"] = "My Test Project";
    ViewData["ProjectDescription"] = "This is Test Project to demo Viewdata and viewbag details";
    ViewData["StartDate"] = new DateTime(2011, 1, 1);
    ViewData["TotalPrice"] = 1000;
    ViewData["TotalDays"] = 100;
    Dictionary<string, string> stackholder = new Dictionary<string, string>();
    stackholder.Add("Client","Mr.  Client");
    stackholder.Add("Manager","Mr. Joy");
    stackholder.Add("Team Leader","Mr.Toy");
    stackholder.Add("Sr. developer", "Mr.dojoy");
    stackholder.Add("developer", "Mr. nodoy");
    ViewData["stackholder"] = stackholder;

    List<string> modules = new List<string>();
    modules.Add("Admin module");
    modules.Add("ShoppingCart module");
    modules.Add("CMS module");
    ViewData["modules"] = modules;
    return View();
}
 
对应UsingViewData View的cshtml:
<h1>@ViewData["Title"]</h1>
 <div>
   <div>
    <h2>Project Name : @ViewData["ProjectName"]</h2>
   </div>
   <div>
     ProjectDescription :   
     <p>"@ViewData["ProjectDescription"]".</p>
   </div>
   <div>
      Stack Holder :
      <br />

      <ul id="stakholder">
      @foreach ( var stakerholder in ViewData["stackholder"] as Dictionary<string, string> )
      {          
    <li>
        @stakerholder.Key &nbsp; : @stakerholder.Value
    </li>
      }
     </ul>
   </div>
   <div>
     Project Details:<br />
     <div>
       module List  :
       <ul id="modulelist">
      @foreach ( var module in ViewData["modules"] as List<string> )
      {          
    <li>
        @module
    </li>
      }
     </ul>
        
     </div>
     Project StartDate : @ViewData["StartDate"]  <br />
     Project TotalPrice: @ViewData["TotalPrice"] <br />
     Project TotaDays  : @ViewData["TotalDays"] 
   </div>
 </div>

 
然后是ViewBag:
public ActionResult UsingViewBag()
{

    ViewBag.Title = " Using ViewBag";
    ViewBag.ProjectName = "My Test Project";
    ViewBag.ProjectDescription = "This is Test Project to demo Viewdata and viewbag details";
    ViewBag.StartDate = new DateTime(2011, 1, 1);
    ViewBag.TotalPrice = 1000;
    ViewBag.TotalDays = 100;
    Dictionary<string, string> stackholder = new Dictionary<string, string>();
    stackholder.Add("Client", "Mr.  Client");
    stackholder.Add("Manager", "Mr. Joy");
    stackholder.Add("Team Leader", "Mr.Toy");
    stackholder.Add("Sr. developer", "Mr.dojoy");
    stackholder.Add("developer", "Mr. nodoy");
    ViewBag.stackholder = stackholder;

    List<string> modules = new List<string>();
    modules.Add("Admin module");
    modules.Add("ShoppingCart module");
    modules.Add("CMS module");
    ViewBag.modules = modules;
    return View();
}
 
对应View UsingViewBag 的cshtml的ViewBag:
<h1>@ViewBag.Title</h1>
 <div>
   <div>
    <h2>Project Name : @ViewBag.ProjectName</h2>
   </div>
   <div>
     ProjectDescription :   
     <p>"@ViewBag.ProjectDescription.</p>
   </div>
   <div>
      Stack Holder :
      <br />

      <ul id="stakholder">
      @foreach ( var stakerholder in ViewBag.stackholder )
      {          
    <li>
        @stakerholder.Key &nbsp; : @stakerholder.Value
    </li>
      }
     </ul>
   </div>
   <div>
     Project Details:<br />
     <div>
       module List  :
       <ul id="modulelist">
      @foreach ( var module in ViewBag.modules )
      {          
    <li>
        @module
    </li>
      }
     </ul>
        
     </div>
     Project StartDate : @ViewBag.StartDate.ToString("dd-MMM-yyyy") <br />
     Project TotalPrice: @ViewBag.TotalPrice  ₹  <br />
     Project TotaDays  : @ViewBag.TotalDays 
   </div>
 </div>

 
后面是在Controller中使用ViewBag:
public ActionResult UsingViewBagInControlAndViewDataInView()
{

    ViewBag.Title = " Using ViewBag In Control And ViewData In View";
    ViewBag.ProjectName = "My Test Project";
    ViewBag.ProjectDescription = "This is Test Project to demo Viewdata and viewbag details";
    ViewBag.StartDate = new DateTime(2011, 1, 1);
    ViewBag.TotalPrice = 1000;
    ViewBag.TotalDays = 100;
    Dictionary<string, string> stackholder = new Dictionary<string, string>();
    stackholder.Add("Client", "Mr.  Client");
    stackholder.Add("Manager", "Mr. Joy");
    stackholder.Add("Team Leader", "Mr.Toy");
    stackholder.Add("Sr. developer", "Mr.dojoy");
    stackholder.Add("developer", "Mr. nodoy");
    ViewBag.stackholder = stackholder;

    List<string> modules = new List<string>();
    modules.Add("Admin module");
    modules.Add("ShoppingCart module");
    modules.Add("CMS module");
    ViewBag.modules = modules;
    return View();
}
 
在UsingViewBagInControlAndViewDataInView.cshtml中使用ViewData来取值：
<h1>@ViewData["Title"]</h1>
 <div>
   <div>
    <h2>Project Name : @ViewData["ProjectName"]</h2>
   </div>
   <div>
     ProjectDescription :   
     <p>"@ViewData["ProjectDescription"]".</p>
   </div>
   <div>
      Stack Holder :
      <br />

      <ul id="stakholder">
      @foreach ( var stakerholder in ViewData["stackholder"] as Dictionary<string, string> )
      {          
    <li>
        @stakerholder.Key &nbsp; : @stakerholder.Value
    </li>
      }
     </ul>
   </div>
   <div>
     Project Details:<br />
     <div>
       module List  :
       <ul id="modulelist">
      @foreach ( var module in ViewData["modules"] as List<string> )
      {          
    <li>
        @module
    </li>
      }
     </ul>
        
     </div>
     Project StartDate : @ViewData["StartDate"]  <br />
     Project TotalPrice: @ViewData["TotalPrice"] <br />
     Project TotaDays  : @ViewData["TotalDays"] 
   </div>
 </div>

 
反过来是这样的: 

  
public ActionResult UsingViewDataInControlAndViewBagInView()
{
    ViewData["Title"] = " Using ViewData In Control And ViewBag In View";
    ViewData["ProjectName"] = "My Test Project";
    ViewData["ProjectDescription"] = "This is Test Project to demo Viewdata and viewbag details";
    ViewData["StartDate"] = new DateTime(2011, 1, 1);
    ViewData["TotalPrice"] = 1000;
    ViewData["TotalDays"] = 100;
    Dictionary<string, string> stackholder = new Dictionary<string, string>();
    stackholder.Add("Client", "Mr.  Client");
    stackholder.Add("Manager", "Mr. Joy");
    stackholder.Add("Team Leader", "Mr.Toy");
    stackholder.Add("Sr. developer", "Mr.dojoy");
    stackholder.Add("developer", "Mr. nodoy");
    ViewData["stackholder"] = stackholder;

    List<string> modules = new List<string>();
    modules.Add("Admin module");
    modules.Add("ShoppingCart module");
    modules.Add("CMS module");
    ViewData["modules"] = modules;
    return View();
}
 
在UsingViewDataInControlAndViewBagInView.cshtml 的View中使用ViewBag来取值:
<h1>@ViewBag.Title</h1>
 <div>
   <div>
    <h2>Project Name : @ViewBag.ProjectName</h2>
   </div>
   <div>
     ProjectDescription :   
     <p>"@ViewBag.ProjectDescription.</p>
   </div>
   <div>
      Stack Holder :
      <br />

      <ul id="stakholder">
      @foreach ( var stakerholder in ViewBag.stackholder )
      {          
    <li>
        @stakerholder.Key &nbsp; : @stakerholder.Value
    </li>
      }
     </ul>
   </div>
   <div>
     Project Details:<br />
     <div>
       module List  :
       <ul id="modulelist">
      @foreach ( var module in ViewBag.modules )
      {          
    <li>
        @module
    </li>
      }
     </ul>
        
     </div>
     Project StartDate : @ViewBag.StartDate.ToString("dd-MMM-yyyy") <br />
     Project TotalPrice: @ViewBag.TotalPrice  ₹  <br />
     Project TotaDays  : @ViewBag.TotalDays 
   </div>
 </div>

 
这样对比看上去会比较清楚一些。在源代码中的ViewBag是这样的属性:
public dynamic ViewBag {
    get {
        if (_dynamicViewData == null) {
            _dynamicViewData = new DynamicViewDataDictionary(() => ViewData);
        }
        return _dynamicViewData;
    }
}
ViewData是：
public ViewDataDictionary ViewData {
    get {
        if (_viewData == null) {
            SetViewData(new ViewDataDictionary());
        }
        return _viewData;
    }
    set {
        SetViewData(value);
    }
}
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原文地址：https://www.cnblogs.com/wangcq/p/3618677.html