NopCommerce Html扩展方法Html.Widget

　　在Nop中有一个Html扩展的类叫HtmlExtensions，主要源码：

public static class HtmlExtensions
    {
        #region Admin area extensions

        public static MvcHtmlString Hint(this HtmlHelper helper, string value)
        {
            // Create tag builder
            var builder = new TagBuilder("img");

            // Add attributes
            var urlHelper = new UrlHelper(helper.ViewContext.RequestContext);
            var url = MvcHtmlString.Create(urlHelper.Content("~/Administration/Content/images/ico-help.gif")).ToHtmlString();

            builder.MergeAttribute("src", url);
            builder.MergeAttribute("alt", value);
            builder.MergeAttribute("title", value);

            // Render tag
            return MvcHtmlString.Create(builder.ToString());
        }

        public static HelperResult LocalizedEditor<T, TLocalizedModelLocal>(this HtmlHelper<T> helper,
            string name,
            Func<int, HelperResult> localizedTemplate,
            Func<T, HelperResult> standardTemplate,
            bool ignoreIfSeveralStores = false)
            where T : ILocalizedModel<TLocalizedModelLocal>
            where TLocalizedModelLocal : ILocalizedModelLocal
        {
            return new HelperResult(writer =>
            {
                var localizationSupported = helper.ViewData.Model.Locales.Count > 1;
                if (ignoreIfSeveralStores)
                {
                    var storeService = EngineContext.Current.Resolve<IStoreService>();
                    if (storeService.GetAllStores().Count >= 2)
                    {
                        localizationSupported = false;
                    }
                }
                if (localizationSupported)
                {
                    var tabStrip = new StringBuilder();
                    tabStrip.AppendLine(string.Format("<div id='{0}'>", name));
                    tabStrip.AppendLine("<ul>");

                    //default tab
                    tabStrip.AppendLine("<li class='k-state-active'>");
                    tabStrip.AppendLine("Standard");
                    tabStrip.AppendLine("</li>");

                    foreach (var locale in helper.ViewData.Model.Locales)
                    {
                        //languages
                        var language = EngineContext.Current.Resolve<ILanguageService>().GetLanguageById(locale.LanguageId);

                        tabStrip.AppendLine("<li>");
                        var urlHelper = new UrlHelper(helper.ViewContext.RequestContext);
                        var iconUrl = urlHelper.Content("~/Content/images/flags/" + language.FlagImageFileName);
                        tabStrip.AppendLine(string.Format("<img class='k-image' alt='' src='{0}'>", iconUrl));
                        tabStrip.AppendLine(HttpUtility.HtmlEncode(language.Name));
                        tabStrip.AppendLine("</li>");
                    }
                    tabStrip.AppendLine("</ul>");



                    //default tab
                    tabStrip.AppendLine("<div>");
                    tabStrip.AppendLine(standardTemplate(helper.ViewData.Model).ToHtmlString());
                    tabStrip.AppendLine("</div>");

                    for (int i = 0; i < helper.ViewData.Model.Locales.Count; i++)
                    {
                        //languages
                        tabStrip.AppendLine("<div>");
                        tabStrip.AppendLine(localizedTemplate(i).ToHtmlString());
                        tabStrip.AppendLine("</div>");
                    }
                    tabStrip.AppendLine("</div>");
                    tabStrip.AppendLine("<script>");
                    tabStrip.AppendLine("$(document).ready(function() {");
                    tabStrip.AppendLine(string.Format("$('#{0}').kendoTabStrip(", name));
                    tabStrip.AppendLine("{");
                    tabStrip.AppendLine("animation:  {");
                    tabStrip.AppendLine("open: {");
                    tabStrip.AppendLine("effects: "fadeIn"");
                    tabStrip.AppendLine("}");
                    tabStrip.AppendLine("}");
                    tabStrip.AppendLine("});");
                    tabStrip.AppendLine("});");
                    tabStrip.AppendLine("</script>");
                    writer.Write(new MvcHtmlString(tabStrip.ToString()));
                }
                else
                {
                    standardTemplate(helper.ViewData.Model).WriteTo(writer);
                }
            });
        }

        public static MvcHtmlString DeleteConfirmation<T>(this HtmlHelper<T> helper, string buttonsSelector) where T : BaseNopEntityModel
        {
            return DeleteConfirmation(helper, "", buttonsSelector);
        }

        public static MvcHtmlString DeleteConfirmation<T>(this HtmlHelper<T> helper, string actionName,
            string buttonsSelector) where T : BaseNopEntityModel
        {
            if (String.IsNullOrEmpty(actionName))
                actionName = "Delete";

            var modalId =  MvcHtmlString.Create(helper.ViewData.ModelMetadata.ModelType.Name.ToLower() + "-delete-confirmation")
                .ToHtmlString();

            var deleteConfirmationModel = new DeleteConfirmationModel
            {
                Id = helper.ViewData.Model.Id,
                ControllerName = helper.ViewContext.RouteData.GetRequiredString("controller"),
                ActionName = actionName,
                WindowId = modalId
            };

            var window = new StringBuilder();
            window.AppendLine(string.Format("<div id='{0}' style='display:none;'>", modalId));
            window.AppendLine(helper.Partial("Delete", deleteConfirmationModel).ToHtmlString());
            window.AppendLine("</div>");
            window.AppendLine("<script>");
            window.AppendLine("$(document).ready(function() {");
            window.AppendLine(string.Format("$('#{0}').click(function (e) ", buttonsSelector));
            window.AppendLine("{");
            window.AppendLine("e.preventDefault();");
            window.AppendLine(string.Format("var window = $('#{0}');", modalId));
            window.AppendLine("if (!window.data('kendoWindow')) {");
            window.AppendLine("window.kendoWindow({");
            window.AppendLine("modal: true,");
            window.AppendLine(string.Format("title: '{0}',", EngineContext.Current.Resolve<ILocalizationService>().GetResource("Admin.Common.AreYouSure")));
            window.AppendLine("actions: ['Close']");
            window.AppendLine("});");
            window.AppendLine("}");
            window.AppendLine("window.data('kendoWindow').center().open();");
            window.AppendLine("});");
            window.AppendLine("});");
            window.AppendLine("</script>");

            return MvcHtmlString.Create(window.ToString());
        }

        public static MvcHtmlString NopLabelFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, bool displayHint = true)
        {
            var result = new StringBuilder();
            var metadata = ModelMetadata.FromLambdaExpression(expression, helper.ViewData);
            var hintResource = string.Empty;
            object value;
            if (metadata.AdditionalValues.TryGetValue("NopResourceDisplayName", out value))
            {
                var resourceDisplayName = value as NopResourceDisplayName;
                if (resourceDisplayName != null && displayHint)
                {
                    var langId = EngineContext.Current.Resolve<IWorkContext>().WorkingLanguage.Id;
                    hintResource = EngineContext.Current.Resolve<ILocalizationService>()
                        .GetResource(resourceDisplayName.ResourceKey + ".Hint", langId);

                    result.Append(helper.Hint(hintResource).ToHtmlString());
                }
            }
            result.Append(helper.LabelFor(expression, new { title = hintResource }));
            return MvcHtmlString.Create(result.ToString());
        }

        public static MvcHtmlString OverrideStoreCheckboxFor<TModel, TValue>(this HtmlHelper<TModel> helper,
            Expression<Func<TModel, bool>> expression,
            Expression<Func<TModel, TValue>> forInputExpression,
            int activeStoreScopeConfiguration)
        {
            var dataInputIds = new List<string>();
            dataInputIds.Add(helper.FieldIdFor(forInputExpression));
            return OverrideStoreCheckboxFor(helper, expression, activeStoreScopeConfiguration, null, dataInputIds.ToArray());
        }
        public static MvcHtmlString OverrideStoreCheckboxFor<TModel, TValue1, TValue2>(this HtmlHelper<TModel> helper,
            Expression<Func<TModel, bool>> expression,
            Expression<Func<TModel, TValue1>> forInputExpression1,
            Expression<Func<TModel, TValue2>> forInputExpression2,
            int activeStoreScopeConfiguration)
        {
            var dataInputIds = new List<string>();
            dataInputIds.Add(helper.FieldIdFor(forInputExpression1));
            dataInputIds.Add(helper.FieldIdFor(forInputExpression2));
            return OverrideStoreCheckboxFor(helper, expression, activeStoreScopeConfiguration, null, dataInputIds.ToArray());
        }
        public static MvcHtmlString OverrideStoreCheckboxFor<TModel, TValue1, TValue2, TValue3>(this HtmlHelper<TModel> helper,
            Expression<Func<TModel, bool>> expression,
            Expression<Func<TModel, TValue1>> forInputExpression1,
            Expression<Func<TModel, TValue2>> forInputExpression2,
            Expression<Func<TModel, TValue3>> forInputExpression3,
            int activeStoreScopeConfiguration)
        {
            var dataInputIds = new List<string>();
            dataInputIds.Add(helper.FieldIdFor(forInputExpression1));
            dataInputIds.Add(helper.FieldIdFor(forInputExpression2));
            dataInputIds.Add(helper.FieldIdFor(forInputExpression3));
            return OverrideStoreCheckboxFor(helper, expression, activeStoreScopeConfiguration, null, dataInputIds.ToArray());
        }
        public static MvcHtmlString OverrideStoreCheckboxFor<TModel>(this HtmlHelper<TModel> helper,
            Expression<Func<TModel, bool>> expression,
            string parentContainer,
            int activeStoreScopeConfiguration)
        {
            return OverrideStoreCheckboxFor(helper, expression, activeStoreScopeConfiguration, parentContainer);
        }
        private static MvcHtmlString OverrideStoreCheckboxFor<TModel>(this HtmlHelper<TModel> helper,
            Expression<Func<TModel, bool>> expression,
            int activeStoreScopeConfiguration,
            string parentContainer = null,
            params string[] datainputIds)
        {
            if (String.IsNullOrEmpty(parentContainer) && datainputIds == null)
                throw new ArgumentException("Specify at least one selector");

            var result = new StringBuilder();
            if (activeStoreScopeConfiguration > 0)
            {
                //render only when a certain store is chosen
                const string cssClass = "multi-store-override-option";
                string dataInputSelector = "";
                if (!String.IsNullOrEmpty(parentContainer))
                {
                    dataInputSelector = "#" + parentContainer + " input, #" + parentContainer + " textarea, #" + parentContainer + " select";
                }
                if (datainputIds != null && datainputIds.Length > 0)
                {
                    dataInputSelector = "#" + String.Join(", #", datainputIds);
                }
                var onClick = string.Format("checkOverriddenStoreValue(this, '{0}')", dataInputSelector);
                result.Append(helper.CheckBoxFor(expression, new Dictionary<string, object>
                {
                    { "class", cssClass },
                    { "onclick", onClick },
                    { "data-for-input-selector", dataInputSelector },
                }));
            }
            return MvcHtmlString.Create(result.ToString());
        }

        /// <summary>
        /// Render CSS styles of selected index 
        /// </summary>
        /// <param name="helper">HTML helper</param>
        /// <param name="currentIndex">Current tab index (where appropriate CSS style should be rendred)</param>
        /// <param name="indexToSelect">Tab index to select</param>
        /// <returns>MvcHtmlString</returns>
        public static MvcHtmlString RenderSelectedTabIndex(this HtmlHelper helper, int currentIndex, int indexToSelect)
        {
            if (helper == null)
                throw new ArgumentNullException("helper");

            //ensure it's not negative
            if (indexToSelect < 0)
                indexToSelect = 0;
            
            //required validation
            if (indexToSelect == currentIndex)
            {
            return new MvcHtmlString(" class='k-state-active'");
            }

            return new MvcHtmlString("");
        }

        #endregion

        #region Common extensions

        public static MvcHtmlString RequiredHint(this HtmlHelper helper, string additionalText = null)
        {
            // Create tag builder
            var builder = new TagBuilder("span");
            builder.AddCssClass("required");
            var innerText = "*";
            //add additional text if specified
            if (!String.IsNullOrEmpty(additionalText))
                innerText += " " + additionalText;
            builder.SetInnerText(innerText);
            // Render tag
            return MvcHtmlString.Create(builder.ToString());
        }

        public static string FieldNameFor<T, TResult>(this HtmlHelper<T> html, Expression<Func<T, TResult>> expression)
        {
            return html.ViewData.TemplateInfo.GetFullHtmlFieldName(ExpressionHelper.GetExpressionText(expression));
        }
        public static string FieldIdFor<T, TResult>(this HtmlHelper<T> html, Expression<Func<T, TResult>> expression)
        {
            var id = html.ViewData.TemplateInfo.GetFullHtmlFieldId(ExpressionHelper.GetExpressionText(expression));
            // because "[" and "]" aren't replaced with "_" in GetFullHtmlFieldId
            return id.Replace('[', '_').Replace(']', '_');
        }

        /// <summary>
        /// Creates a days, months, years drop down list using an HTML select control. 
        /// The parameters represent the value of the "name" attribute on the select control.
        /// </summary>
        /// <param name="html">HTML helper</param>
        /// <param name="dayName">"Name" attribute of the day drop down list.</param>
        /// <param name="monthName">"Name" attribute of the month drop down list.</param>
        /// <param name="yearName">"Name" attribute of the year drop down list.</param>
        /// <param name="beginYear">Begin year</param>
        /// <param name="endYear">End year</param>
        /// <param name="selectedDay">Selected day</param>
        /// <param name="selectedMonth">Selected month</param>
        /// <param name="selectedYear">Selected year</param>
        /// <param name="localizeLabels">Localize labels</param>
        /// <returns></returns>
        public static MvcHtmlString DatePickerDropDowns(this HtmlHelper html,
            string dayName, string monthName, string yearName,
            int? beginYear = null, int? endYear = null,
            int? selectedDay = null, int? selectedMonth = null, int? selectedYear = null, bool localizeLabels = true)
        {
            var daysList = new TagBuilder("select");
            var monthsList = new TagBuilder("select");
            var yearsList = new TagBuilder("select");

            daysList.Attributes.Add("name", dayName);
            monthsList.Attributes.Add("name", monthName);
            yearsList.Attributes.Add("name", yearName);

            var days = new StringBuilder();
            var months = new StringBuilder();
            var years = new StringBuilder();

            string dayLocale, monthLocale, yearLocale;
            if (localizeLabels)
            {
                var locService = EngineContext.Current.Resolve<ILocalizationService>();
                dayLocale = locService.GetResource("Common.Day");
                monthLocale = locService.GetResource("Common.Month");
                yearLocale = locService.GetResource("Common.Year");
            }
            else
            {
                dayLocale = "Day";
                monthLocale = "Month";
                yearLocale = "Year";
            }

            days.AppendFormat("<option value='{0}'>{1}</option>", "0", dayLocale);
            for (int i = 1; i <= 31; i++)
                days.AppendFormat("<option value='{0}'{1}>{0}</option>", i,
                    (selectedDay.HasValue && selectedDay.Value == i) ? " selected="selected"" : null);


            months.AppendFormat("<option value='{0}'>{1}</option>", "0", monthLocale);
            for (int i = 1; i <= 12; i++)
            {
                months.AppendFormat("<option value='{0}'{1}>{2}</option>",
                                    i, 
                                    (selectedMonth.HasValue && selectedMonth.Value == i) ? " selected="selected"" : null,
                                    CultureInfo.CurrentUICulture.DateTimeFormat.GetMonthName(i));
            }


            years.AppendFormat("<option value='{0}'>{1}</option>", "0", yearLocale);

            if (beginYear == null)
                beginYear = DateTime.UtcNow.Year - 100;
            if (endYear == null)
                endYear = DateTime.UtcNow.Year;

            if (endYear > beginYear)
            {
                for (int i = beginYear.Value; i <= endYear.Value; i++)
                    years.AppendFormat("<option value='{0}'{1}>{0}</option>", i,
                        (selectedYear.HasValue && selectedYear.Value == i) ? " selected="selected"" : null);
            }
            else
            {
                for (int i = beginYear.Value; i >= endYear.Value; i--)
                    years.AppendFormat("<option value='{0}'{1}>{0}</option>", i,
                        (selectedYear.HasValue && selectedYear.Value == i) ? " selected="selected"" : null);
            }

            daysList.InnerHtml = days.ToString();
            monthsList.InnerHtml = months.ToString();
            yearsList.InnerHtml = years.ToString();

            return MvcHtmlString.Create(string.Concat(daysList, monthsList, yearsList));
        }

        public static MvcHtmlString Widget(this HtmlHelper helper, string widgetZone, object additionalData = null)
        {
            return helper.Action("WidgetsByZone", "Widget", new { widgetZone = widgetZone, additionalData = additionalData });
        }

        /// <summary>
        /// Renders the standard label with a specified suffix added to label text
        /// </summary>
        /// <typeparam name="TModel">Model</typeparam>
        /// <typeparam name="TValue">Value</typeparam>
        /// <param name="html">HTML helper</param>
        /// <param name="expression">Expression</param>
        /// <param name="htmlAttributes">HTML attributes</param>
        /// <param name="suffix">Suffix</param>
        /// <returns>Label</returns>
        public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, object htmlAttributes, string suffix)
        {
            string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
            var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
            string resolvedLabelText = metadata.DisplayName ?? (metadata.PropertyName ?? htmlFieldName.Split(new [] { '.' }).Last());
            if (string.IsNullOrEmpty(resolvedLabelText))
            {
                return MvcHtmlString.Empty;
            }
            var tag = new TagBuilder("label");
            tag.Attributes.Add("for", TagBuilder.CreateSanitizedId(html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(htmlFieldName)));
            if (!String.IsNullOrEmpty(suffix))
            {
                resolvedLabelText = String.Concat(resolvedLabelText, suffix);
            }
            tag.SetInnerText(resolvedLabelText);

            var dictionary = ((IDictionary<string, object>)HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
            tag.MergeAttributes(dictionary, true);

            return MvcHtmlString.Create(tag.ToString(TagRenderMode.Normal));
        }

        #endregion
    }

主要是看Widget这个扩展方法

 public static MvcHtmlString Widget(this HtmlHelper helper, string widgetZone, object additionalData = null)
        {
            return helper.Action("WidgetsByZone", "Widget", new { widgetZone = widgetZone, additionalData = additionalData });
        }

添加这个类后，就可以在cshtml页面中直接@Html.Widget了

看Widget实现，还是调用的Action方法，第一个参数action名字，第二参数Controller

找到WidgetController下面的WidgetsByZone方法

   
[ChildActionOnly]
public ActionResult WidgetsByZone(string widgetZone, object additionalData = null)
        {
            var cacheKey = string.Format(ModelCacheEventConsumer.WIDGET_MODEL_KEY, _storeContext.CurrentStore.Id, widgetZone);
            var cacheModel = _cacheManager.Get(cacheKey, () =>
            {
                //model
                var model = new List<RenderWidgetModel>();

                var widgets = _widgetService.LoadActiveWidgetsByWidgetZone(widgetZone, _storeContext.CurrentStore.Id);
                foreach (var widget in widgets)
                {
                    var widgetModel = new RenderWidgetModel();

                    string actionName;
                    string controllerName;
                    RouteValueDictionary routeValues;
                    widget.GetDisplayWidgetRoute(widgetZone, out actionName, out controllerName, out routeValues);
                    widgetModel.ActionName = actionName;
                    widgetModel.ControllerName = controllerName;
                    widgetModel.RouteValues = routeValues;

                    model.Add(widgetModel);
                }
                return model;
            });

            //no data?
            if (cacheModel.Count == 0)
                return Content("");

            //"RouteValues" property of widget models depends on "additionalData".
            //We need to clone the cached model before modifications (the updated one should not be cached)
            var clonedModel = new List<RenderWidgetModel>();
            foreach (var widgetModel in cacheModel)
            {
                var clonedWidgetModel = new RenderWidgetModel();
                clonedWidgetModel.ActionName = widgetModel.ActionName;
                clonedWidgetModel.ControllerName = widgetModel.ControllerName;
                if (widgetModel.RouteValues != null)
                    clonedWidgetModel.RouteValues = new RouteValueDictionary(widgetModel.RouteValues);

                if (additionalData != null)
                {
                    if (clonedWidgetModel.RouteValues == null)
                        clonedWidgetModel.RouteValues = new RouteValueDictionary();
                    clonedWidgetModel.RouteValues.Add("additionalData", additionalData);
                }

                clonedModel.Add(clonedWidgetModel);
            }

            return PartialView(clonedModel);
        }

[ChildActionOnly]
Child action 和 Patial view 类似，也是在应用程序的不同地方可以重复利用相同的子内容。不同的是，它是通过调用 controller 中的 action 方法来呈现子内容的，并且一般包含了业务的处理。任何 action 都可以作为子 action 。接下来介绍如何使用它。详细信息请见 http://www.cnblogs.com/willick/archive/2013/11/14/3410855.html

 var widgets = _widgetService.LoadActiveWidgetsByWidgetZone(widgetZone, _storeContext.CurrentStore.Id);

这个WidgetByZone就是查找当前已使用的@Html.Widget（“xxx”）并返回相应的控制器名字，方法名和路由值

打开试图WidgetWidgetsByZone.cshtml

@model List<RenderWidgetModel>
@using Nop.Web.Models.Cms;
@foreach (var widget in Model)
{
    @Html.Action(widget.ActionName, widget.ControllerName, widget.RouteValues)
}

这个视图的目的就是循环输出html，具体输出的内容在插件里面实现的，比如插件Nop.Plugin.Widgets.NivoSlider里面有个NivoSliderPlugin，这类插件必须继承自BasePlugin,和IWidgetPlugin，里面的方法GetDisplayWidgetRoute就是用于返回显示这个插件内容的action的信息，WidgetsNivoSliderController.cs里面的public ActionResult PublicInfo(string widgetZone)就是这个插件具体输出的内容，大体流程就是这样了。