MVC中 ViewData、ViewBag、TempData的区别与联系
ViewData和TempData都可以传递弱类型数据，区别如下:
ViewData 只在当前 Action 中有效，生命周期和 View 相同；
TempData 的数据至多只能经过一次Controller传递，并且每个元素至多只能被访问一次，访问以后，自动被删除。
TempData 一般用于临时的缓存内容或抛出错误页面时传递错误信息，可以将TempData 在使用之前存储到相应的 ViewData 中以备循环使用。
TempData 保存在Session中，Controller每次执行请求的时候，会从Session中先获取 TempData，而后清除Session，获取完TempData数据，虽然保存在内部字典对象中，但是其集合中的每个条目访问一次后就从字典表中删 除。具体代码层面，TempData获取过程是通过SessionStateTempDataProvider.LoadTempData方法从 ControllerContext的Session中读取数据，而后清除Session，故TempData只能跨Controller传递一次。
Index
public ActionResult Index()
{
ViewBag.Message = "Welcome to ASP.NET MVC!";
ViewData["myName"] = "我的名字";
TempData["myAgeOne"] = "26岁";
TempData["myAgeTwo"] = "27岁";
return View();
}姓名：@ViewData["myName"]
年龄1：@TempData["myAgeOne"]
About
姓名：@ViewData["myName"]
年龄1：@TempData["myAgeOne"]
年龄2：@TempData["myAgeTwo"]
ViewBag和ViewData区别与联系如下:
ViewBag.Name=ViewData["Name"];
相同：使用同一个字典集合（数据源）
不同：ViewBag 是 MVC3 新增语法，ViewBag 不再是字典的键值对结构，而是 dynamic 动态类型，它会在程序运行的时候动态解析。
三者相比之下ViewBag 和ViewData生命周期相同，也是对但前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，属于Mvc3里面新增的部分。
具体请看以下代码:
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 : @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.Titleh1> <div> <div> <h2>Project Name : @ViewBag.ProjectNameh2> div> <div> ProjectDescription : <p>"@ViewBag.ProjectDescription.p> div> <div> Stack Holder : <br /> <ul id="stakholder"> @foreach ( var stakerholder in ViewBag.stackholder ) { <li> @stakerholder.Key : @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 : @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.Titleh1> <div> <div> <h2>Project Name : @ViewBag.ProjectNameh2> div> <div> ProjectDescription : <p>"@ViewBag.ProjectDescription.p> div> <div> Stack Holder : <br /> <ul id="stakholder"> @foreach ( var stakerholder in ViewBag.stackholder ) { <li> @stakerholder.Key : @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); } }
具体细节在这儿不深入了，这里只是抛砖引玉。希望对您Asp.net MVC开发有帮助。