Author: Chris F Carroll

These overloads will do the hopefully-obvious thing with a Model => Model.Property and a List of SelectListItems (or a single SelectListItem)

Use the RadioButtonLabelLayout setting to control whether you nest the radio button inside its label, or lay them out as siblings; and whether you like text before button or vice versa.

    public static class HtmlHelperRadioButtonExtensions
    {
        /// <summary>
        /// Returns radio buttons for the property in the object represented by the specified expression.
        /// A radio button is rendered for each item in <paramref name="listOfValues"/>.
        /// Use <paramref name="labelLayout"/> to control whether each label contains its button, or is a sibling, 
        /// and whether button precedes text or vice versa.
        /// <list type="bullet">
        /// <item>
        ///     <term>Example result for the default labelLayout= RadioButtonLabelLayout.LabelTagContainsButtonThenText:</term>
        ///     <description>
        ///     &lt;label for="Object_Property_Red"&gt;&lt;input id="Object_Property_Red" name="Object.Property" type="radio" value="Red" /&gt; Red&lt;/label&gt; 
        ///     &lt;label for="Object_Property_Blue"&gt;&lt;input id="Object_Property_Blue" name="Object.Property" type="radio" value="Blue" /&gt; Blue&lt;/label&gt; 
        ///     </description>
        /// </item>
        /// <item>
        ///     <term>Example result for labelLayout= RadioButtonLabelLayout.SiblingBeforeButton:</term>
        ///     <description>
        ///     &lt;label for="Object_Property_Red"&gt;Red&lt;/label&gt; &lt;input id="Object_Property_Red" name="Object.Property" type="radio" value="Red" /&gt;
        ///     &lt;label for="Object_Property_Blue"&gt; Blue&lt;/label&gt; &lt;input id="Object_Property_Blue" name="Object.Property" type="radio" value="Blue" /&gt;
        ///     </description>
        /// </item>
        /// </list>
        /// </summary>
        /// <param name="listOfValues">Used to generate the Value and the Label Text for each radio button</param>
        /// <param name="labelLayout">One <see cref="RadioButtonLabelLayout"/> to control the layout of the rendered button and its label.</param>
        /// <returns>
        /// An MvcHtmlString for the required buttons 
        /// 
        /// </returns>
        public static MvcHtmlString 
            RadioButtonsFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper,
                                                    Expression<Func<TModel, TProperty>> expression,
                                                    IEnumerable<SelectListItem> listOfValues,
                                                    RadioButtonLabelLayout labelLayout = RadioButtonLabelLayout.LabelTagContainsButtonThenText)
        {
            if (listOfValues == null) { return null; }
            var buttons= listOfValues.Select(item => RadioButtonFor(htmlHelper, expression, item, labelLayout));
            return MvcHtmlString.Create(buttons.Aggregate(new StringBuilder(), (sb, o) => sb.Append(o), sb => sb.ToString()));
        }

        /// <summary> Create an <see cref="IEnumerable{T}"/> list of radio buttons ready for individual processing before rendering</summary>
        public static IEnumerable<MvcHtmlString> RadioButtonListFor<TModel, TProperty>(
                    this HtmlHelper<TModel> htmlHelper,
                    Expression<Func<TModel, TProperty>> expression,
                    IEnumerable<SelectListItem> listOfValues,
                    RadioButtonLabelLayout labelLayout)
        {
            if (listOfValues == null) { return new MvcHtmlString[0]; }
            return listOfValues.Select( item =>  RadioButtonFor(htmlHelper, expression, item, labelLayout) );
        }

        public static MvcHtmlString RadioButtonFor<TModel, TProperty>(
                                HtmlHelper<TModel> htmlHelper, 
                                Expression<Func<TModel, TProperty>> expression, 
                                SelectListItem item, 
                                RadioButtonLabelLayout labelLayout)
        {
            var id = htmlHelper.IdFor(expression) + " " + item.Value;
            var radio = htmlHelper.RadioButtonFor(expression, item.Value, new {id}).ToHtmlString();
            var labelText = HttpUtility.HtmlEncode(item.Text);
            TagBuilder nestingLabel = null;
            switch (labelLayout)
            {
                case RadioButtonLabelLayout.LabelTagContainsTextThenButton:
                    nestingLabel = new TagBuilder("label") {InnerHtml = labelText + " " + radio};
                    return MvcHtmlString.Create(nestingLabel.ToString());
                case RadioButtonLabelLayout.LabelTagContainsButtonThenText:
                    nestingLabel = new TagBuilder("label") {InnerHtml = radio + " " + labelText};
                    return MvcHtmlString.Create(nestingLabel.ToString());
                case RadioButtonLabelLayout.SiblingBeforeButton:
                    return MvcHtmlString.Create(radio + " " + htmlHelper.Label(id, labelText));
                case RadioButtonLabelLayout.SiblingAfterButton:
                    return MvcHtmlString.Create(htmlHelper.Label(id, labelText) + " " + radio);
                default:
                    throw new ArgumentOutOfRangeException("labelLayout", labelLayout, 
                                "This is not a valid RadioButtonLayoutStyle for rendering a radio button");
            }
        }
    }

    public enum RadioButtonLabelLayout
    {
        LabelTagContainsButtonThenText = 0,
        LabelTagContainsTextThenButton = 1,
        SiblingBeforeButton = 2,
        SiblingAfterButton = 3,
    }