ViewBag中的對象

我已經開始使用MVC 3，我非常喜歡使用它。在許多層面上，這比WebForms更好的體驗。ViewBag中的對象

但是我有一個關於ViewBag（新ViewData）的問題我非常小心地堅持聲音建模實踐，我傾向於將視圖需要的所有東西放到ViewModels中。然而，就ViewBag而言，除了糟糕的建模實踐之外，是否還有其他顧慮，表明應該謹慎使用ViewBag？我自己並沒有太多的使用它，但是隊友今天提出了這個問題，我只能推薦限制它的使用，因爲它是一個弱類型模型，被動態地使用動態（sudo類型）

我可以告訴那裏使用它不應該有任何性能影響？我對不對？這只是另一個應用於視圖服務器端的對象。我不指望使用動態的任何性能影響（如果有一個可以測量的）

對於使用ViewBag的缺點（甚至是優點），您有什麼看法？

來源

2012-03-30 TGH

對我來說，最大的問題是ViewBag不是類型安全的，如果你不小心的話，很容易產生運行時錯誤。

視圖包真的只是一個方便，以防止簡單的情況下，否則你需要一個新的視圖模型。我經常使用它們，但僅限於非常簡單的數據。

來源

2012-03-30 04:35:07

是的，我同意，這似乎很像一個好地方到另一個地方追悔沒來，當你做你的視圖模型，或者沒有適合。我通常將它用於簡單的事情，如int或其他一些簡單的對象。 – TGH 2012-03-30 04:37:24

從我的文章在： 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!

來源

2012-03-30 05:40:15

ViewBag中的對象

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