ViewBag vs MVC中的ViewData

http://royalarun.blogspot.in/2013/08/viewbag-viewdata-tempdata-and-view.html

ViewBag和ViewData的相似之处:

当您从控制器移动到视图时，有助于维护数据。用于 将数据从控制器传递到相应的视图。短寿命意味着 值在重定向发生时变为空。这是因为他们的目标 是提供一种在控制器和视图之间通信的方法。这是 服务器调用中的通信机制。

ViewBag和ViewData的区别:

ViewData是派生自的对象字典 viewdatdictionary类，并使用字符串作为键访问。ViewBag 动态属性是否利用了新的动态特性 在c# 4.0。ViewData需要对复杂的数据类型进行类型转换 检查空值以避免错误。ViewBag不需要 复杂数据类型的类型转换。

ViewBag & ViewData示例:

public ActionResult Index()
{   
    ViewBag.Name = "Arun Prakash";   
    return View();
}

public ActionResult Index()
{  
    ViewData["Name"] = "Arun Prakash";  
    return View();
}   

视图呼叫

@ViewBag.Name    
@ViewData["Name"]

ViewData用于将数据从控制器传递给ViewData，它是从viewdatdictionary类派生出来的。仅对当前请求可用。仅要求复杂数据类型的类型转换，并检查null值以避免错误。如果发生重定向，则其值为null

ViewBag是一个动态属性，它利用了c# 4.0中的新动态特性。它也仅对当前请求可用。如果发生重定向，则其值为null

下面是关于ViewData, ViewBag, TempData和Session的点对点差异。 信贷/ askforprogram复制。在这里，遵循我没有提到的代码示例的链接。

ViewData in MVC ViewData is property of ControllerBase class. ViewData is a type of dictionary object. ViewData is key-value dictionary collection. ViewData was introduced in MVC 1.0 version. ViewData works with .Net framework 3.5 and above. Need to do type conversion of code while enumerating. ViewData object keeps data only for current request. ViewBag in MVC ViewBag is property of ControllerBase class. ViewBag is a type of dynamic object. ViewBag is a type of object. ViewBag was introduced in MVC 3.0 version. ViewBag works with .Net framework 4.0 and above. ViewBag uses property and handles it, so no need to do type conversion while enumerating. ViewBag object keeps data only for current request. TempData in MVC TempData is property of ControllerBase class. TempData is a type of dictionary object. TempData is key-value dictionary collection. TempData was introduced in MVC 1.0 version. TempData works with .Net framework 3.5 and above. Need to do type conversion of code while enumerating. TempData object is used to data between current request and subsequent request. Session in MVC Session is property of Controller(Abstract Class). Session is a type of HttpSessionStateBase. Session is key-value dictionary collection. Session was introduced in MVC 1.0 version. TempData works with .Net framework 1.0 and above. Need to do type conversion of code while enumerating. Session object keeps data for all requests. Valid for all requests, never expires.

它使用c# 4.0动态特性。它实现了与viewdata相同的目标，应该避免使用强类型视图模型(与viewdata应该避免的方式相同)。

基本上它取代了魔法字符串:

ViewData["Foo"]

具有神奇属性:

ViewBag.Foo

你没有编译时安全性。

我继续指责微软在MVC中引入了这个概念。

属性的名称区分大小写。

在ViewBag内部，属性以名称/值对的形式存储在ViewData字典中。

注意:在MVC 3的大多数预发布版本中，ViewBag属性被命名为ViewModel，这段代码来自MVC 3发布说明:

有人建议我发布我发布的这个信息的来源，下面是来源: http://www.asp.net/whitepapers/mvc3-release-notes#_Toc2_4

MVC 2 controllers support a ViewData property that enables you to pass data to a view template using a late-bound dictionary API. In MVC 3, you can also use somewhat simpler syntax with the ViewBag property to accomplish the same purpose. For example, instead of writing ViewData["Message"]="text", you can write ViewBag.Message="text". You do not need to define any strongly-typed classes to use the ViewBag property. Because it is a dynamic property, you can instead just get or set properties and it will resolve them dynamically at run time. Internally, ViewBag properties are stored as name/value pairs in the ViewData dictionary. (Note: in most pre-release versions of MVC 3, the ViewBag property was named the ViewModel property.)

所有的答案都表明ViewBag和/或ViewData是将数据从控制器传递到视图，这是错误的信息。两者都非常有用，可以将数据从视图传递到布局或局部视图(或ViewComponents等)。它不是控制器专属的。

默认的asp.net示例在布局页面中有:

<title>@ViewData["Title"] - MyApp</title>

在任何情况下

ViewData["Title"] = "Details";

然后，问这个问题:“ViewBag和ViewData之间有什么区别?”

最显著的区别是ViewData是一个强类型字典 ViewBag是一个动态类型。

注意里面的数据IS the SAME

ViewData["Title"] = "MyTitle";
ViewBag.Title; // returns "MyTitle";

什么时候用这个或那个?

ViewBag doesn't support not valid C# names. you can't access ViewData["Key With Space"] with ViewBag ViewBag.Something is dynamic and you may have problems when calling methods (like extension methods) that needs to know the exact parameter at compile time. ViewBag can check for nulls syntactical cleaner: ViewBag.Person?.Name ViewData have all the properties of a Dictionary like ContainsKey, Add, etc. so you can use ViewData.Add("somekey", "somevalue") keep in mind it might throw exceptions. Using ViewData on views needs TypeCasting while ViewBag don't.

知道了细微的差别，使用其中一种更像是一种口味偏好。

通常你可以想到ViewBag。ViewData别名的任意键["AnyKey"]