如何扩展 MVC3 标签和 LabelFor HTML 助手？

Question

Html.Label 和 Html.LabelFor 辅助方法不像大多数其他辅助方法那样支持 htmlAttributes 参数。但是，我想设置class。像这样的：

Html.LabelFor(model => model.Name, new { @class = "control-label" })

有没有一种简单的方法来扩展 Label/LabelFor 而不复制和扩展这些方法的 ILSpy disasm 输出？

Answer 1

您可以通过创建自己的 LabelFor 轻松扩展标签：

这样的事情应该可以满足您的需要

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

更新 要使用刚刚在您的项目中创建的扩展方法，请将此行添加到您的 Views\web.config

<pages>
  <namespaces>
    <add namespace="System.Web.Helpers" />
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    <add namespace="System.Web.Routing" />
    <add namespace="System.Web.WebPages" />
    <add namespace="MyProject.Helpers" />   <-- my extension

    ...

 </namespaces>
</pages>

Answer 2

public static class LabelExtensions
{
    public static IHtmlString LabelFor<TModel, TProperty>(
        this HtmlHelper<TModel> htmlHelper,
        Expression<Func<TModel, TProperty>> expression,
        string labelText,
        object htmlAttributes
    )
    {
        var metadata = ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, htmlHelper.ViewData);
        var htmlFieldName = ExpressionHelper.GetExpressionText(expression);
        return LabelHelper(htmlHelper, metadata, htmlFieldName, labelText, htmlAttributes);
    }

    public static IHtmlString Label(this HtmlHelper htmlHelper, string expression, string labelText, object htmlAttributes)
    {
        var metadata = ModelMetadata.FromStringExpression(expression, htmlHelper.ViewData);
        return LabelHelper(htmlHelper, metadata, expression, labelText, htmlAttributes);
    }

    private static IHtmlString LabelHelper(HtmlHelper html, ModelMetadata metadata, string htmlFieldName, string labelText, object htmlAttributes)
    {
        string str = labelText ?? (metadata.DisplayName ?? (metadata.PropertyName ?? htmlFieldName.Split(new char[] { '.' }).Last<string>()));
        if (string.IsNullOrEmpty(str))
        {
            return MvcHtmlString.Empty;
        }
        TagBuilder tagBuilder = new TagBuilder("label");
        tagBuilder.Attributes.Add("for", TagBuilder.CreateSanitizedId(html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName)));
        var attributes = new RouteValueDictionary(htmlAttributes);
        tagBuilder.MergeAttributes(attributes);
        tagBuilder.SetInnerText(str);
        return new HtmlString(tagBuilder.ToString(TagRenderMode.Normal));
    }
}

然后：

@Html.LabelFor(x => x.SomeProperty, null, new { @class = "foo" })

或：

@Html.Label("SomeProperty", null, new { @class = "foo" })