?????? ?使用強(qiáng)類型的ViewData好處有許多，比如說在IDE中就會(huì)有更好的支持，比如代碼提示。同時(shí)在View與Controller之間有更嚴(yán)謹(jǐn)?shù)摹凹s定”。在Suteki.Shop項(xiàng)目中作者對強(qiáng)類型的ViewPage引入是通過MvcContrib實(shí)現(xiàn)的，下面就是其ViewPage<T>代碼（Suteki.Shop\Views\ViewPage.cs）：????? ? public?class?ViewPage<T>?:?MvcContrib.FluentHtml.ModelViewPage<T>?where?T?:?class?
{
????????public?ViewPage()?:?base(new?LowercaseFirstCharacterOfNameBehaviour())
????????{}
}

public?class?ViewUserControl<T>?:?MvcContrib.FluentHtml.ModelViewUserControl<T>?where?T?:?class
{
????????public?ViewUserControl()?:?base(new?LowercaseFirstCharacterOfNameBehaviour())
????????{}
}
??????? ?可以看出ViewPage和ViewUserControl只是對MvcContrib中ModelViewPage，ModelViewUserControl的繼承，代碼很簡單，沒什么太多可說的。 ?????? ?強(qiáng)類型的ViewData使用形如：ViewPage<TViewData>，我們可以通過打開一個(gè)View看一下，比如“編輯用戶信息”時(shí)的視圖頭聲明部分：
?????? <%@?Page?Title=""?Language="C#"??Inherits="Suteki.Shop.ViewPage<ShopViewData>"
?????????其中的ShopViewData就是TViewData。在Suteki.Shop中作者使用ShopViewData對Model中大部分類作了相應(yīng)的屬性和數(shù)據(jù)綁定的統(tǒng)一封裝，感覺ShopViewData就是Model的集合體或者是“縮影”，這樣的好處就我看來主要是在View中進(jìn)行強(qiáng)類型ViewData綁定時(shí)統(tǒng)一參數(shù)，這里感覺有偷懶之嫌。不過因此造成其自身視圖數(shù)據(jù)的“庸腫”，其內(nèi)部有太多的屬性，還是就是綁定傳遞時(shí)的效率可能也會(huì)存在一些問題（只是猜測，未測試過，呵呵）。 ???????? 好了，下面就開始正文。
???
???????? 首先我們要看一下Suteki.Common\ViewData文件夾下面的幾個(gè)類，包括：
????
??????? ?IErrorViewData，IMessageViewData，ViewDataBase等，其類圖如下：
????
????????
????
??????? ?從圖中看出，ViewDataBase是其體系“核心”， 其實(shí)現(xiàn)了 IMessageViewData, IErrorViewData這兩個(gè)接口。其實(shí)體代碼如下：??? ? public?abstract?class?ViewDataBase?:?IMessageViewData,?IErrorViewData
{
????????public?string?Message?{?get;?set;?}
????????public?string?ErrorMessage?{?get;?set;?}

????????public?ViewDataBase?WithErrorMessage(string?errorMessage)
????????{
????????????this.ErrorMessage?=?errorMessage;
????????????return?this;
????????}

????????public?ViewDataBase?WithMessage(string?message)
????????{
????????????this.Message?=?message;
????????????return?this;
????????}
} ??? ??????? ?該抽象類的屬性Message，ErrorMessage分別實(shí)現(xiàn)了IMessageViewData和IErrorViewData的接口屬性。主要?用于顯示臨時(shí)操作信息（比如“成功添加用戶”，“成功編輯用戶”等）。其所提供的兩個(gè)方法“WithErrorMessage”?和“WithMessage”只是對相應(yīng)屬性的簡單綁定而已。
??
??????? 有了ViewDataBase之后，下面就來看一下其子類實(shí)現(xiàn)了，下面是相應(yīng)類圖：
????
????
?????? ?正如前面所介紹的那樣，子類中最“重要”的當(dāng)屬“ShopViewData”，其包括了基本所有Model中的類型，并將它們以“屬性”的方法提供出來以便于前臺View使用，同時(shí)ShopViewData還提供了與其屬性相關(guān)的綁定方法（均以“With...”開頭），下面就是其代碼。??? ? Code
public?class?ShopViewData?:?ViewDataBase
{
????????public?Category?Category?{?get;?set;?}
????????public?IEnumerable<Category>?Categories?{?get;?set;?}

????????public?Product?Product?{?get;?set;?}
????????public?IEnumerable<Product>?Products?{?get;?set;?}

????????public?IEnumerable<Role>?Roles?{?get;?set;?}

????????public?User?User?{?get;?set;?}
????????public?IEnumerable<User>?Users?{?get;?set;?}

????????public?Basket?Basket?{?get;?set;?}

????????public?Order?Order?{?get;?set;?}
????????public?PagedList<Order>?Orders?{?get;?set;?}
????????public?OrderSearchCriteria?OrderSearchCriteria?{?get;?set;?}

????????public?IEnumerable<Country>?Countries?{?get;?set;?}
????????public?Country?Country?{?get;?set;?}

????????public?IEnumerable<CardType>?CardTypes?{?get;?set;?}

????????public?Postage?Postage?{?get;?set;?}
????????public?IEnumerable<Postage>?Postages?{?get;?set;?}

????????public?PostageResult?PostageResult?{?get;?set;?}

????????public?Card?Card?{?get;?set;?}

????????public?IEnumerable<StockItem>?StockItems?{?get;?set;?}

????????public?IEnumerable<Content>?Contents?{?get;?set;?}

????????public?IEnumerable<OrderStatus>?OrderStatuses?{?get;?set;?}

????????//?attempt?at?a?fluent?interface

????????public?ShopViewData?WithCategory(Category?category)
????????{
????????????this.Category?=?category;
????????????return?this;
????????}

????????public?ShopViewData?WithCategories(IEnumerable<Category>?categories)
????????{
????????????this.Categories?=?categories;
????????????return?this;
????????}

????????public?ShopViewData?WithProduct(Product?product)
????????{
????????????this.Product?=?product;
????????????return?this;
????????}

????????public?ShopViewData?WithProducts(IEnumerable<Product>?products)
????????{
????????????this.Products?=?products;
????????????return?this;
????????}

????????public?ShopViewData?WithRoles(IEnumerable<Role>?roles)
????????{
????????????this.Roles?=?roles;
????????????return?this;
????????}

????????public?ShopViewData?WithUser(User?user)
????????{
????????????this.User?=?user;
????????????return?this;
????????}

????????public?ShopViewData?WithUsers(IEnumerable<User>?users)
????????{
????????????this.Users?=?users;
????????????return?this;
????????}

????????public?ShopViewData?WithBasket(Basket?basket)
????????{
????????????this.Basket?=?basket;
????????????return?this;
????????}

????????public?ShopViewData?WithOrders(PagedList<Order>?orders)
????????{
????????????this.Orders?=?orders;
????????????return?this;
????????}

????????public?ShopViewData?WithOrder(Order?order)
????????{
????????????this.Order?=?order;
????????????return?this;
????????}

????????public?ShopViewData?WithOrderSearchCriteria(OrderSearchCriteria?orderSearchCriteria)
????????{
????????????this.OrderSearchCriteria?=?orderSearchCriteria;
????????????return?this;
????????}

????????public?ShopViewData?WithCountries(IEnumerable<Country>?countries)
????????{
????????????this.Countries?=?countries;
????????????return?this;
????????}

????????public?ShopViewData?WithCountry(Country?country)
????????{
????????????this.Country?=?country;
????????????return?this;
????????}

????????public?ShopViewData?WithCardTypes(IEnumerable<CardType>?cardTypes)
????????{
????????????this.CardTypes?=?cardTypes;
????????????return?this;
????????}

????????public?ShopViewData?WithPostage(Postage?postage)
????????{
????????????this.Postage?=?postage;
????????????return?this;
????????}

????????public?ShopViewData?WithPostages(IEnumerable<Postage>?postages)
????????{
????????????this.Postages?=?postages;
????????????return?this;
????????}

????????public?ShopViewData?WithTotalPostage(PostageResult?postageResult)
????????{
????????????this.PostageResult?=?postageResult;
????????????return?this;
????????}

????????public?ShopViewData?WithCard(Card?card)
????????{
????????????this.Card?=?card;
????????????return?this;
????????}

????????public?ShopViewData?WithStockItems(IEnumerable<StockItem>?stockItems)
????????{
????????????this.StockItems?=?stockItems;
????????????return?this;
????????}

????????public?ShopViewData?WithContents(IEnumerable<Content>?contents)
????????{
????????????this.Contents?=?contents;
????????????return?this;
????????}

????????public?ShopViewData?WithOrderStatuses(IEnumerable<OrderStatus>?orderStatuses)
????????{
????????????this.OrderStatuses?=?orderStatuses;
????????????return?this;
????????}
} ????
???????? 為了便于使用，Suteki.Shop還以靜態(tài)屬性的方式進(jìn)行了封閉，最終以ShopView這個(gè)類開放出來提供給Action和View使用，其實(shí)現(xiàn)代碼如下：???? ? ///?<summary>
///?So?you?can?write?
///?ShopView.Data.WithProducts(myProducts);
///?</summary>
public?class?ShopView
{
?????public?static?ShopViewData?Data?{?get?{?return?new?ShopViewData();?}?}
}

?????? ? 下面以“編輯用戶”這個(gè)Action來看一下其使用方法：? [AcceptVerbs(HttpVerbs.Post),?UnitOfWork]
public?ActionResult?Edit([DataBind]?User?user,?string?password)
{
????????if(!?string.IsNullOrEmpty(password))
????????{
????????????user.Password?=?userService.HashPassword(password);
????????}

????????try
????????{
????????????user.Validate();
????????}
????????catch?(ValidationException?validationException)
????????{
????????????validationException.CopyToModelState(ModelState,?"user");
????????????return?View("Edit",?EditViewData.WithUser(user));
????????}

????????return?View("Edit",?EditViewData.WithUser(user).WithMessage("Changes?have?been?saved"));?
} ??? ??????? ?注意其中的EditViewData屬性就是初始化一個(gè)ShopViewData實(shí)例并調(diào)用該實(shí)例的WithRoles（）方法來完成對用戶規(guī)則的獲取。然后在"Edit"這個(gè)Action的返回語句中繼續(xù)綁定其他信息，如當(dāng)前編輯的用戶信息“user”,以及操作提示信息“Changes have been saved”。 ?????? ? 這樣就可以在View中對ShopViewData進(jìn)行顯示操作了。這里要說明的是在View中對Message的顯示是通過下面這一行完成的：????? ? <%=?Html.MessageBox(ViewData.Model)?%>

???????? 而這個(gè)方法是對HtmlHelper這個(gè)MVC類的擴(kuò)展方法，其方法定義如下：?? public?static?string?MessageBox(this?HtmlHelper?htmlHelper,?IMessageViewData?messageViewData)
{
????if?(messageViewData.Message?==?null)?return?string.Empty;

????HtmlTextWriter?writer?=?new?HtmlTextWriter(new?StringWriter());

????writer.AddAttribute("class",?"message");
????writer.RenderBeginTag(HtmlTextWriterTag.Div);
????writer.Write(messageViewData.Message);
????writer.RenderEndTag();
????return?writer.InnerWriter.ToString();
}
??????? ? 大家看到了其傳入的參數(shù)是IMessageViewData類型，而傳入的是“ShopViewData”類型，如下圖所示：
?????? ??????? 而看過上面內(nèi)容的話，就可以通過其類圖中實(shí)現(xiàn)的方法看出這個(gè)繼承實(shí)現(xiàn)鏈表：? ??????ShopViewData?==>?ViewDataBase?==?>?IMessageViewData
????
???????? 所以擴(kuò)展文法直接就完成了這種“向上轉(zhuǎn)型”操作。????
????
?????? ??除了“編輯用戶”這種在Action中直接綁定Message字段屬性的方式，Suteki.Shop還提供了Filter方式的“操作信息”綁定，比如CopyMessageFromTempDataToViewData（Suteki.Shop\Filters)，其代碼如下： ? public?class?CopyMessageFromTempDataToViewData?:?ActionFilterAttribute
{
????????public?override?void?OnActionExecuted(ActionExecutedContext?filterContext)?
????????{
????????????????var?result?=?filterContext.Result?as?ViewResult;

????????????????if(result?!=?null?&&?filterContext.Controller.TempData.ContainsKey("message"))
????????????????{
????????????????????var?model?=?result.ViewData.Model?as?ShopViewData;

????????????????????if(model?!=?null?&&?string.IsNullOrEmpty(model.Message))
????????????????????{
????????????????????????model.Message?=?filterContext.Controller.TempData["message"]?as?string;
????????????????????}
????????????????}
????????}
}
????
????
??? ???? 大家請注意，上面的filterContext.Controller類型是ControllerBase（詳細(xì)說明參見我之前寫的這篇文章），其提供了Message屬性來實(shí)現(xiàn)臨時(shí)數(shù)據(jù)TempData["message"]的獲取來綁定工作，代碼如下： [Rescue("Default"),?Authenticate,?CopyMessageFromTempDataToViewData]
public?abstract?class?ControllerBase?:?Controller,?IProvidesBaseService
{
????????
????????
?????public?string?Message
?????{
?????????get?{?return?TempData["message"]?as?string;?}
?????????set?{?TempData["message"]?=?value;?}
?????}
}
????
???????? 這樣就可以通過CopyMessageFromTempDataToViewData這個(gè)Filter來實(shí)現(xiàn)將臨時(shí)數(shù)據(jù)綁定到ShopViewData中的Message屬性，并提供給前臺View使用了。當(dāng)然這是有條件的，就是上面代碼中的這一行：
????if(model?!=?null?&&?string.IsNullOrEmpty(model.Message))?
???????? 從邏輯上看，這樣做應(yīng)該是防止對已綁定操作信息（model.Message不為空）進(jìn)行“誤覆蓋”吧。
???
???
?????? ? 好了，今天的內(nèi)容就先到這里了。
????
??????
????
????
???
????
????
????
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轉(zhuǎn)載于:https://blog.51cto.com/daizhj/160560

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