为什么我找不到RadioButtonFor方法？

Question

这是我的静态类:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Mvc;
using System.Linq.Expressions;
using System.Text;
using System.Web;

namespace Foo.WebUI.Infrastructure
{
    public static class HtmlHelpers
    {
        public static MvcHtmlString Image(this HtmlHelper helper, string src, string altText)
        {
            var builder = new TagBuilder("img");
            builder.MergeAttribute("src", src);
            builder.MergeAttribute("alt", altText);

            return MvcHtmlString.Create(builder.ToString(TagRenderMode.SelfClosing));
        }

        public static MvcHtmlString RadioButtonForEnum<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
        {
            var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
            var names = Enum.GetNames(metaData.ModelType);
            var sb = new StringBuilder();
            foreach (var name in names)
            {
                var id = string.Format(
                    "{0}_{1}_{2}",
                    htmlHelper.ViewData.TemplateInfo.HtmlFieldPrefix,
                    metaData.PropertyName,
                    name
                );

 //---------------------------------------ERROR HERE!-----------------------------
                var radio = htmlHelper.RadioButtonFor(expression, name, new { id = id }).ToHtmlString();
                sb.AppendFormat(
                    "<label for=\"{0}\">{1}</label> {2}",
                    id,
                    HttpUtility.HtmlEncode(name),
                    radio
                );
            }
            return MvcHtmlString.Create(sb.ToString());
        }

    }
}

当我编译它时,我收到此错误:

'System.Web.Mvc.HtmlHelper'不包含'RadioButtonFor'的定义,并且没有扩展方法'RadioButtonFor'接受类型为'System.Web.Mvc.HtmlHelper'的第一个参数'(你是否缺少using指令)或汇编参考？

我从这个答案得到了这个辅助方法:

将枚举传递给html.radiobuttonfor MVC3

Answer 1

该InputExtensions.RadioButtonFor扩展方法是在System.Web.Mvc.Html命名空间,所以你需要添加一个using子句这个命名空间