为什么我找不到 RadioButtonFor 方法？
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”不包含以下定义 'RadioButtonFor' 且没有扩展方法 'RadioButtonFor' 接受 “System.Web.Mvc.HtmlHelper”类型的第一个参数可以是 找到（您是否缺少 using 指令或程序集引用？
我从这个答案中得到了这个辅助方法：
Here is my static class:
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());
}
}
}
When I compile this, I get this error:
'System.Web.Mvc.HtmlHelper' does not contain a definition for
'RadioButtonFor' and no extension method 'RadioButtonFor' accepting a
first argument of type 'System.Web.Mvc.HtmlHelper' could be
found (are you missing a using directive or an assembly reference?
I got this helper method from this answer:
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评论（4）
InputExtensions.RadioButtonFor扩展方法位于System 中.Web.Mvc.Html命名空间，因此需要为此命名空间添加using子句The
InputExtensions.RadioButtonForextension method is in theSystem.Web.Mvc.Htmlnamespace, so you need to add ausingclause for this namespace将
using System.Web.Mvc.Html;添加到代码顶部add
using System.Web.Mvc.Html;to the top of your codeRadioButtonForEnum方法不是HtmlHelper类的一部分，它是一个扩展。您必须包含扩展类所在的命名空间：您可以在 该方法的文档页面。
The
RadioButtonForEnummethod is not a part of theHtmlHelperclass, it's an extension. You have to include the namespace where the extension class is:You can see the namespace to use on the documentation page for the method.
为了使其始终可访问，您可以在
Views\Web.config文件中添加对 HtmlHelper 命名空间的引用，如下所示，以便它始终在您的视图中可见，而不必每次都包含它时间。To make this always accessible, you can add a reference to your HtmlHelper namspace in your
Views\Web.configfile as below, so that it will always be visible from your views, without having to include it every time.