ASP.NET MVC3 向View传递数据

我们可以通过ViewResult 使Action传递数据到View.

一般来说我们使用3种方式通过Action向View传递数据：

1.ViewData

2.TempData

3.强类型Model 

我们先来看看ViewContext，其有3个Virtual 属性：

public class ViewContext : ControllerContext
{
  public virtual TempDataDictionary TempData { get; set; }
  public virtual IView View { get; set; }
  public virtual ViewDataDictionary ViewData { get; set; }
　...
} 

ViewData TempData传递过程：

Action中的赋值语句实际上操作的是Controller类的ViewData和TempData属性, 此时并没有任何的数据传递.Action返回ViewResult,

 Controller的View方法会将Controller类的ViewData和TempData属性值传递给ViewResult,代码如下:

public abstract class Controller : ControllerBase, IActionFilter,IAuthorizationFilter, IDisposable, IExceptionFilter, IResultFilter
{
...
protected internal virtual ViewResult View(IView view, object model)
{
    if (model != null)
    {
        base.ViewData.Model = model;
    }
    return new ViewResult { View = view, ViewData = base.ViewData, TempData = base.TempData };
}
...
}

 ViewResult的ExecuteResult根据ViewData和TempData构建ViewContext对象:

public abstract class ViewResultBase : ActionResult
{
...
public override void ExecuteResult(ControllerContext context)
{
    if (context == null)
    {
        throw new ArgumentNullException("context");
    }
    if (string.IsNullOrEmpty(this.ViewName))
    {
        this.ViewName = context.RouteData.GetRequiredString("action");
    }
    ViewEngineResult result = null;
    if (this.View == null)
    {
        result = this.FindView(context);
        this.View = result.View;
    }
    TextWriter writer = context.HttpContext.get_Response().get_Output();
    ViewContext viewContext = new ViewContext(context, this.View, this.ViewData, this.TempData, writer);
    this.View.Render(viewContext, writer);
    if (result != null)
    {
        result.ViewEngine.ReleaseView(context, this.View);
    }
}
...
}

ViewContext对象最终会传递给ViewPage, 也就是说ViewData和TempData集合传递到了ViewPage.  实际上ViewData对象并不是通过ViewContext传递到ViewPage中的。

ViewPage上的ViewData是一个单独的属性,它继承自：IVeiwContainer

public interface IViewDataContainer
{
    // Properties
    ViewDataDictionary ViewData { get; set; }
}

TempData在Controller的基类ControllerBase中定义

public abstract class ControllerBase : IController
{
... 
public TempDataDictionary TempData
{
    get
    {
        if ((this.ControllerContext != null) && this.ControllerContext.IsChildAction)
        {
            return this.ControllerContext.ParentActionViewContext.TempData;
        }
        if (this._tempDataDictionary == null)
        {
            this._tempDataDictionary = new TempDataDictionary();
        }
        return this._tempDataDictionary;
    }
    set
    {
        this._tempDataDictionary = value;
    }
}
 ...
}

TempData其实访问的是ViewContext.TempData

ViewPage Code如下：

[FileLevelControlBuilder(typeof(ViewPageControlBuilder))]
public class ViewPage : Page, IViewDataContainer
{
　　...
　　public ViewDataDictionary ViewData
　　{
    　　get
    　　{
        　　if (this._viewData == null)
        　　{
            　　this.SetViewData(new ViewDataDictionary());
       　　 }
        　　return this._viewData;
    　　}
    　　set
    　　{
        　　this.SetViewData(value);
    　　}
　　}
　　public TempDataDictionary TempData
　　{
    　　get
    　　{
        　　return this.ViewContext.TempData;
    　　}
　　}
　　...
}

ViewData 和TempData传值如下：

public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ViewData["ViewData"] = "ViewData";
            TempData["TempData"] = "TempData";
            return View();
        }
    }

 在View中我们如下使用：

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
ViewData传值:<%=ViewData["ViewData"]%><br />
TempData传值:<%=TempData["TempData"]%>
</asp:Content>

ViewData只能在当前Action中有效
TempData可以类似于Session一样到其它页面仍然存在,但仅仅局限于这两个前后相连的页面(只能经过一次Controller传递)

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 

强类型Model传值如下：

1. 我们需要Create一个Model类：

 public class Movie
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Director { get; set; }
    }

2. Create一个View:

ViewName:Index

Check:Cerate aStrongly-typed view

选择刚Create的Movie Model

Scaffold template:选择List

点击ADD创建View

VS自动生成如下Code:

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<Jeriffe.Web.MVC.MovieApp.Movie>" %>
<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    Details
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<h2>Details</h2>
<fieldset>
    <legend>Movie</legend>
    <div class="display-label">Title</div>
    <div class="display-field">
        <%: Html.DisplayFor(model => model.Title) %>
    </div>
    <div class="display-label">Director</div>
    <div class="display-field">
        <%: Html.DisplayFor(model => model.Director) %>
    </div>
</fieldset>
<p>
    <%: Html.ActionLink("Edit", "Edit", new { id=Model.Id }) %> |
    <%: Html.ActionLink("Back to List", "Index") %>
</p>
</asp:Content>

 ViewPage的Model属性就是一个强类型对象, 在这里就是Movie.page页面指令可以看出, 这里的页面继承自ViewPage<Model>类, 而不是ViewPage.

ViewPage<TModel> Code如下：

public class ViewPage<TModel> : ViewPage
{
    // Fields
    private ViewDataDictionary<TModel> _viewData;

    // Methods
    public ViewPage();
    public override void InitHelpers();
    protected override void SetViewData(ViewDataDictionary viewData);

    // Properties
    public AjaxHelper<TModel> Ajax { get; set; }
    public HtmlHelper<TModel> Html { get; set; }
    public TModel Model { get; }
    public ViewDataDictionary<TModel> ViewData { get; set; }
}