截止上篇文章asp.net mvc源码分析-ActionResult篇 RazorView.RenderView 相信大家对mvc的大致流程应该有所了解。现在我们来看看我们在mvc开发中用的最多的几个方法，我想排在第一的应该是Html.RenderAction和Html.RenderPartial吧。先说简单的吧：RenderPartial和Partial

 public static void RenderPartial(this HtmlHelper htmlHelper, string partialViewName, object model, ViewDataDictionary viewData) {
            htmlHelper.RenderPartialInternal(partialViewName, viewData, model,htmlHelper.ViewContext.Writer, ViewEngines.Engines);
        }

  public static MvcHtmlString Partial(this HtmlHelper htmlHelper, string partialViewName, object model, ViewDataDictionary viewData) {
            using (StringWriter writer = new StringWriter(CultureInfo.CurrentCulture)) {
                htmlHelper.RenderPartialInternal(partialViewName, viewData, model,writer, ViewEngines.Engines);
                return MvcHtmlString.Create(writer.ToString());
            }
        }

从这里我们可以知道RenderPartial和Partial它们返回的东西写到的流不一致，一个是当前的writer，一个是新建的writer，当然新建的writer便于返回字符文本。

  internal virtual void RenderPartialInternal(string partialViewName, ViewDataDictionary viewData, object model, TextWriter writer, ViewEngineCollection viewEngineCollection) {
            if (String.IsNullOrEmpty(partialViewName)) {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "partialViewName");
            }
            ViewDataDictionary newViewData = null;
            if (model == null) {
                if (viewData == null) {
                    newViewData = new ViewDataDictionary(ViewData);
                }
                else {
                    newViewData = new ViewDataDictionary(viewData);
                }
            }
            else {
                if (viewData == null) {
                    newViewData = new ViewDataDictionary(model);
                }
                else {
                    newViewData = new ViewDataDictionary(viewData) { Model = model };
                }
            }


            ViewContext newViewContext = new ViewContext(ViewContext, ViewContext.View, newViewData, ViewContext.TempData, writer);
            IView view = FindPartialView(newViewContext, partialViewName, viewEngineCollection);
            view.Render(