asp.net-mvc 如何覆盖 @Html.LabelFor 模板？

How can I override the @Html.LabelFor template?

提问by balexandre

I have a simple field form

我有一个简单的字段表单

<div class="field fade-label">
    @Html.LabelFor(model => model.Register.UserName)
    @Html.TextBoxFor(model => model.Register.UserName)
</div>

and this results in:

这导致：

<div class="field fade-label">
    <label for="Register_UserName">Username (used to identify all services, from 4 to 30 chars)</label>
    <input type="text" value="" name="Register.UserName" id="Register_UserName">
</div>

but I want that LabelForcode append a <span>inside so I can end up having:

但我希望该LabelFor代码在<span>内部附加一个，这样我最终可以拥有：

<label for="Register_UserName">
    <span>Username (used to identify all services, from 4 to 30 chars)</span>
</label>

How can I do this?

我怎样才能做到这一点？

All examplesuse EditorTemplatesbut this is a LabelFor.

所有示例都使用，EditorTemplates但这是一个LabelFor.

回答by Bryan S.

You'd do this by creating your own HTML helper.

您可以通过创建自己的 HTML 帮助程序来完成此操作。

http://www.asp.net/mvc/tutorials/creating-custom-html-helpers-cs

http://www.asp.net/mvc/tutorials/creating-custom-html-helpers-cs

You can view the code for LabelFor<> by downloading the source for ASP.Net MVC and modify that as a custom helper.

您可以通过下载 ASP.Net MVC 的源代码来查看 LabelFor<> 的代码，并将其修改为自定义帮助程序。

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Answeradded by balexandre

balexandre添加的答案

public static class LabelExtensions
{
    public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, object htmlAttributes)
    {
        return LabelFor(html, expression, new RouteValueDictionary(htmlAttributes));
    }
    public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, IDictionary<string, object> htmlAttributes)
    {
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
        string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
        string labelText = metadata.DisplayName ?? metadata.PropertyName ?? htmlFieldName.Split('.').Last();
        if (String.IsNullOrEmpty(labelText))
        {
            return MvcHtmlString.Empty;
        }

        TagBuilder tag = new TagBuilder("label");
        tag.MergeAttributes(htmlAttributes);
        tag.Attributes.Add("for", html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(htmlFieldName));

        TagBuilder span = new TagBuilder("span");
        span.SetInnerText(labelText);

        // assign <span> to <label> inner html
        tag.InnerHtml = span.ToString(TagRenderMode.Normal);

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

回答by Setarcos

I expanded upon balealexandre's answer and added in the ability to specify HTML to include both before and after your label text. I added a bunch of method overloads and comments. I hope this helps folks!

我扩展了 balealexandre 的答案，并添加了指定 HTML 以在标签文本之前和之后包含的功能。我添加了一堆方法重载和注释。我希望这可以帮助人们！

Also snagged information from here: Html inside label using Html helper

还从这里获取信息： Html inside label using Html helper

namespace System.Web.Mvc.Html
{
    public static class LabelExtensions
    {
        /// <summary>Creates a Label with custom Html before the label text.  Only starting Html is provided.</summary>
        /// <param name="startHtml">Html to preempt the label text.</param>
        /// <returns>MVC Html for the Label</returns>
        public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, Func<object, HelperResult> startHtml)
        {
            return LabelFor(html, expression, startHtml, null, new RouteValueDictionary("new {}"));
        }

        /// <summary>Creates a Label with custom Html before the label text.  Starting Html and a single Html attribute is provided.</summary>
        /// <param name="startHtml">Html to preempt the label text.</param>
        /// <param name="htmlAttributes">A single Html attribute to include.</param>
        /// <returns>MVC Html for the Label</returns>
        public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, Func<object, HelperResult> startHtml, object htmlAttributes)
        {
            return LabelFor(html, expression, startHtml, null, new RouteValueDictionary(htmlAttributes));
        }

        /// <summary>Creates a Label with custom Html before the label text.  Starting Html and a collection of Html attributes are provided.</summary>
        /// <param name="startHtml">Html to preempt the label text.</param>
        /// <param name="htmlAttributes">A collection of Html attributes to include.</param>
        /// <returns>MVC Html for the Label</returns>
        public static MvcHtmlString LabelFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression, Func<object, HelperResult> startHtml, IDictionary<string, object> htmlAttributes)
        {
            return LabelFor(html, expression, startHtml, null, htmlAttributes);
        }

        /// <summary>Creates a Label with custom Html before and after the label text.  Starting Html and ending Html are provided.</summary>
        /// <param name="startHtml">Html to preempt the label text.</param>
        /// <param name="endHtml">Html to follow the label text.</param>
        /// <returns>MVC Html for the Label</returns>
        public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, Func<object, HelperResult> startHtml, Func<object, HelperResult> endHtml)
        {
            return LabelFor(html, expression, startHtml, endHtml, new RouteValueDictionary("new {}"));
        }

        /// <summary>Creates a Label with custom Html before and after the label text.  Starting Html, ending Html, and a single Html attribute are provided.</summary>
        /// <param name="startHtml">Html to preempt the label text.</param>
        /// <param name="endHtml">Html to follow the label text.</param>
        /// <param name="htmlAttributes">A single Html attribute to include.</param>
        /// <returns>MVC Html for the Label</returns>
        public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, Func<object, HelperResult> startHtml, Func<object, HelperResult> endHtml, object htmlAttributes)
        {
            return LabelFor(html, expression, startHtml, endHtml, new RouteValueDictionary(htmlAttributes));
        }

        /// <summary>Creates a Label with custom Html before and after the label text.  Starting Html, ending Html, and a collection of Html attributes are provided.</summary>
        /// <param name="startHtml">Html to preempt the label text.</param>
        /// <param name="endHtml">Html to follow the label text.</param>
        /// <param name="htmlAttributes">A collection of Html attributes to include.</param>
        /// <returns>MVC Html for the Label</returns>
        public static MvcHtmlString LabelFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression, Func<object, HelperResult> startHtml, Func<object, HelperResult> endHtml, IDictionary<string, object> htmlAttributes)
        {
            ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
            string htmlFieldName = ExpressionHelper.GetExpressionText(expression);

            //Use the DisplayName or PropertyName for the metadata if available.  Otherwise default to the htmlFieldName provided by the user.
            string labelText = metadata.DisplayName ?? metadata.PropertyName ?? htmlFieldName.Split('.').Last();
            if (String.IsNullOrEmpty(labelText))
            {
                return MvcHtmlString.Empty;
            }

            //Create the new label.
            TagBuilder tag = new TagBuilder("label");

            //Add the specified Html attributes
            tag.MergeAttributes(htmlAttributes);

            //Specify what property the label is tied to.
            tag.Attributes.Add("for", html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(htmlFieldName));

            //Run through the various iterations of null starting or ending Html text.
            if (startHtml == null && endHtml == null) tag.InnerHtml = labelText;
            else if (startHtml != null && endHtml == null) tag.InnerHtml = string.Format("{0}{1}", startHtml(null).ToHtmlString(), labelText);
            else if (startHtml == null && endHtml != null) tag.InnerHtml = string.Format("{0}{1}", labelText, endHtml(null).ToHtmlString());
            else tag.InnerHtml = string.Format("{0}{1}{2}", startHtml(null).ToHtmlString(), labelText, endHtml(null).ToHtmlString());

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

回答by Darren Lewis

LabelFor is an extension method (static) and therefore cannot be overridden. You'd need to create your own Html Helper Extension method to achieve what you require.

LabelFor 是一个扩展方法（静态），因此不能被覆盖。您需要创建自己的 Html Helper Extension 方法来实现您的需求。