【Asp.net MVC源码解读】View Render Order

 

1. The ViewResult returned from an action method executes.
   
2. The ViewResult uses the IViewEngine to find the view.
   
3. The ViewResult creates a ViewContext from the ControllerContext, view name, view data, and temp data.
   
4. The ViewResult calls Render() on the IView located by the IViewEngine. (the rest of the steps are specific to the WebFormView).
   
5. The WebFormView uses IBuildManager to create a ViewPage or ViewUserControl from a virtual path.
   
6. The WebFormView sets the MasterLocation on the ViewPage, sets the ViewData and calls RenderView() passing in the ViewContext.
   
7. The ViewPage saves off the ViewContext, initializes HtmlHelper, AjaxHelper, and UrlHelper and then delegates to base.ProcessRequest(), which you are already familiar with since it is the method on IHttpHandler.
   From the time an action method returns a ViewResult

 

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namespace System.Web.Mvc {
    using System;
    using System.Globalization;
    using System.IO;
    using System.Web.Mvc.Resources;

    public class WebFormView : IView {

        private IBuildManager _buildManager;

        public WebFormView(string viewPath)
            : this(viewPath, null) {
        }

        public WebFormView(string viewPath, string masterPath) {
            if (String.IsNullOrEmpty(viewPath)) {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "viewPath");
            }

            ViewPath = viewPath;
            MasterPath = masterPath ?? String.Empty;
        }

        internal IBuildManager BuildManager {
            get {
                if (_buildManager == null) {
                    _buildManager = new BuildManagerWrapper();
                }
                return _buildManager;
            }
            set {
                _buildManager = value;
            }
        }

        public string MasterPath {
            get;
            private set;
        }

        public string ViewPath {
            get;
            private set;
        }

        public virtual void Render(ViewContext viewContext, TextWriter writer) {
            if (viewContext == null) {
                throw new ArgumentNullException("viewContext");
            }

            object viewInstance = BuildManager.CreateInstanceFromVirtualPath(ViewPath, typeof(object));
            if (viewInstance == null) {
                throw new InvalidOperationException(
                    String.Format(
                        CultureInfo.CurrentUICulture,
                        MvcResources.WebFormViewEngine_ViewCouldNotBeCreated,
                        ViewPath));
            }

            ViewPage viewPage = viewInstance as ViewPage;
            if (viewPage != null) {
                RenderViewPage(viewContext, viewPage);
                return;
            }

            ViewUserControl viewUserControl = viewInstance as ViewUserControl;
            if (viewUserControl != null) {
                RenderViewUserControl(viewContext, viewUserControl);
                return;
            }

            throw new InvalidOperationException(
                String.Format(
                    CultureInfo.CurrentUICulture,
                    MvcResources.WebFormViewEngine_WrongViewBase,
                    ViewPath));
        }

        private void RenderViewPage(ViewContext context, ViewPage page) {
            if (!String.IsNullOrEmpty(MasterPath)) {
                page.MasterLocation = MasterPath;
            }

            page.ViewData = context.ViewData;
            page.RenderView(context);
        }

        private void RenderViewUserControl(ViewContext context, ViewUserControl control) {
            if (!String.IsNullOrEmpty(MasterPath)) {
                throw new InvalidOperationException(MvcResources.WebFormViewEngine_UserControlCannotHaveMaster);
            }

            control.ViewData = context.ViewData;
            control.RenderView(context);
        }
    }
}