ViewBag中的对象

我已经开始使用MVC 3，我非常喜欢使用它。在许多层面上，这比WebForms更好的体验。ViewBag中的对象

但是我有一个关于ViewBag（新ViewData）的问题我非常小心地坚持声音建模实践，我倾向于将视图需要的所有东西放到ViewModels中。然而，就ViewBag而言，除了糟糕的建模实践之外，是否还有其他顾虑，表明应该谨慎使用ViewBag？我自己并没有太多的使用它，但是队友今天提出了这个问题，我只能推荐限制它的使用，因为它是一个弱类型模型，被动态地使用动态（sudo类型）

我可以告诉那里使用它不应该有任何性能影响？我对不对？这只是另一个应用于视图服务器端的对象。我不指望使用动态的任何性能影响（如果有一个可以测量的）

对于使用ViewBag的缺点（甚至是优点），您有什么看法？

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2012-03-30 TGH

对我来说，最大的问题是ViewBag不是类型安全的，如果你不小心的话，很容易产生运行时错误。

视图包真的只是一个方便，以防止简单的情况下，否则你需要一个新的视图模型。我经常使用它们，但仅限于非常简单的数据。

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2012-03-30 04:35:07

是的，我同意，这似乎很像一个好地方到另一个地方追悔没来，当你做你的视图模型，或者没有适合。我通常将它用于简单的事情，如int或其他一些简单的对象。 – TGH 2012-03-30 04:37:24

从我的文章在： http://completedevelopment.blogspot.com/2011/12/stop-using-viewbag-in-most-places.html

Even the built in templates give us support for ViewBag. The scaffolding templates create ViewBag.SomeEnumerable to use for our pages.
Sure - its quick code and since it's auto-generated will likely work ok. The problem comes in from the fact that ViewBag is a dynamic object. There are no compile time type checks. If you misspell something you won't be notified from the compiler.

I've seen this used in such bad ways, I would love to see it's usage curbed and applications cleaned up.

So in a controller:
ViewBag.SomeProperty = "10"
and in the view:
@ViewBag.Som3Pr0p3rty
We won't ever know of this error. It won't even generate a runtime error since the misspelled name just generated a null.

Use ViewModels and save yourself from these potential problems. Our templates set a page title in ViewBag as well.

There are several options in setting a page title. Since this is a well known property one could argue that using it just for Title is ok. I wouldn't argue this. There are other options.
1. Set it in a section in the layout and render it from the client.
2. Use ViewBag.Title
3. Use a filter (seems much too complicated for a title)
4. Use a Model.Title field.

Since by default we have a ViewBag.Title field created and our templates also get it by default, I'll yield that in this case, its ok.

What about select lists?
Rather than the default

ViewBag.CustomerId = new SelectList(db.Customers, "CustomerId", "FirstName", order.CustomerId);

Do something like
yourViewModel.Customers = customers; //a loaded collection

and in your view
@Html.DropDownListFor(x => x.CustomerId, new SelectList(Model.Customers, "CustomerId", "Name"))

Or if you prefer to set your ViewModel to contain the SelectList

yourViewModel.Customers = new SelectList(db.Customers, "CustomerId", "Name", order.CustomerId);

and now your view would be slightly cleaner as:
@Html.DropDownListFor(x => x.CustomerId, x.Customers)

See, that's not so difficult now is it? Enjoy!

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2012-03-30 05:40:15

ViewBag中的对象

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