asp.net-mvc-3 - MVC3 - 将 NEW-LINE 传递给 ModelState.AddModelError

Question

当后端发生错误时，MVC Controller 通过
返回消息 ModelState.AddModelError("", "message");

我希望该“消息”以 2 行显示，因此我想添加一个 "\r\n"
或"<br />" 介于两者之间。

我正在使用 Razor 使用 @Html.ValidationSummary(); 显示消息
但 View 的 HTML 输出将其显示为 <br/>

在消息上传递换行符并将其解释为 HTML 输出级别的真实
标记的最佳方法是什么？

==================================
Controller 代码:

ModelState.AddModelError("", "Line one <br /> Line two.");
return Request.IsAjaxRequest() ? (ActionResult) PartialView("ViewName", model) 
            : View(model);

查看代码:

@using (Ajax.BeginForm("Index", "Home", new AjaxOptions { UpdateTargetId = "tv" })) 
{
    @if (Html.ValidationSummary() != null)
        @Html.Raw(Server.HtmlDecode(Html.ValidationSummary(true).ToString()))   

    ....
}

Answer 1

ValidationSummary 帮助程序 HTML 对错误消息进行编码，这是设计使然。这意味着您不能使用 HTML 标签，因为它们将被编码。所以你可以编写一个不编码的自定义助手:

public static class ValidationExtensions
{
    public static IHtmlString MyValidationSummary(this HtmlHelper htmlHelper)
    {
        var formContextForClientValidation = htmlHelper.ViewContext.ClientValidationEnabled ? htmlHelper.ViewContext.FormContext : null;
        if (htmlHelper.ViewData.ModelState.IsValid)
        {
            if (formContextForClientValidation == null)
            {
                return null;
            }
            if (htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled)
            {
                return null;
            }
        }

        var stringBuilder = new StringBuilder();
        var ulBuilder = new TagBuilder("ul");

        ModelState modelState;
        if (htmlHelper.ViewData.ModelState.TryGetValue(htmlHelper.ViewData.TemplateInfo.HtmlFieldPrefix, out modelState))
        {
            foreach (ModelError error in modelState.Errors)
            {
                string userErrorMessageOrDefault = error.ErrorMessage;
                if (!string.IsNullOrEmpty(userErrorMessageOrDefault))
                {
                    var liBuilder = new TagBuilder("li");
                    liBuilder.InnerHtml = userErrorMessageOrDefault;
                    stringBuilder.AppendLine(liBuilder.ToString(TagRenderMode.Normal));
                }
            }
        }

        if (stringBuilder.Length == 0)
        {
            stringBuilder.AppendLine("<li style=\"display:none\"></li>");
        }
        ulBuilder.InnerHtml = stringBuilder.ToString();

        TagBuilder divBuilder = new TagBuilder("div");
        divBuilder.AddCssClass(htmlHelper.ViewData.ModelState.IsValid ? HtmlHelper.ValidationSummaryValidCssClassName : HtmlHelper.ValidationSummaryCssClassName);
        divBuilder.InnerHtml = ulBuilder.ToString(TagRenderMode.Normal);
        if (formContextForClientValidation != null)
        {
            if (!htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled)
            {
                divBuilder.GenerateId("validationSummary");
                formContextForClientValidation.ValidationSummaryId = divBuilder.Attributes["id"];
                formContextForClientValidation.ReplaceValidationSummary = false;
            }
        }
        return new HtmlString(divBuilder.ToString(TagRenderMode.Normal));
    }
}

然后:

@Html.MyValidationSummary()

我们的自定义帮助程序中的以下行明确不进行 HTML 编码:

liBuilder.InnerHtml = userErrorMessageOrDefault;

在原来的助手中，它看起来像这样:

liBuilder.SetInnerText(userErrorMessageOrDefault);