自定义 Html 助手在 asp.net MVC 2.0 中不起作用

Question

我在 asp.net mvc 1.0 中使用了这个自定义 html 帮助程序，但现在我尝试在 2.0 项目中使用它并且它崩溃了

http://blog.pagedesigners.co.nz/archive/2009/07/15/asp.net-mvc-ndash-validation-summary-with-2-forms-amp-1.aspx

这是我得到的错误。

System.MissingMethodException was unhandled by user code
  Message=Method not found: 'System.String System.Web.Mvc.Html.ValidationExtensions.ValidationSummary(System.Web.Mvc.HtmlHelper)'.
  Source=CustomHtmlHelpers
  StackTrace:
       at CustomHtmlHelpers.ActionValidationSummaryHelper.ActionValidationSummary(HtmlHelper html, String action)
       at ASP.views_signin_signin_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in  SignIn.aspx:line 23
       at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
       at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer)
       at System.Web.UI.Control.Render(HtmlTextWriter writer)
       at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
       at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter)
       at System.Web.UI.Control.RenderControl(HtmlTextWriter writer)
       at ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer)   Site.Master:line 64
       at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
       at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer)
       at System.Web.UI.Control.Render(HtmlTextWriter writer)
       at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
       at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter)
       at System.Web.UI.Control.RenderControl(HtmlTextWriter writer)
       at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
       at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer)
       at System.Web.UI.Page.Render(HtmlTextWriter writer)
       at System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer)
       at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
       at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter)
       at System.Web.UI.Control.RenderControl(HtmlTextWriter writer)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
  InnerException: 

我在同一个库中的其他 html 助手确实可以工作。我将命名空间添加到 webconfig 中。

我拥有的代码

 public static class ActionValidationSummaryHelper
    {
        public static MvcHtmlString ActionValidationSummary(this HtmlHelper html, string action)
        {
            string currentAction = html.ViewContext.RouteData.Values["action"].ToString();

            if (currentAction.ToLower() == action.ToLower())
            {
                return html.ValidationSummary();
            }

            return MvcHtmlString.Empty;
        }

    }

Answer 1

它抱怨它找不到返回字符串的 ValidationSummery 方法......所以我认为这可能是因为 HtmlHelper.ValidationSummary() 现在返回 MvcHtmlString 的实例而不是 System.String。

我没有对此进行测试，但请尝试将您的扩展方法更改为：

public static MvcHtmlString ActionValidationSummary(this HtmlHelper html, string action)
{
    string currentAction = html.ViewContext.RouteData.Values["action"].ToString();

    if (currentAction.ToLower() == action.ToLower())
        return html.ValidationSummary();

    return MvcHtmlString.Empty;
}

让我知道这是否有效:-)

HTH，
查尔斯