Check Box List Class in Asp.Net MVC

public static partial class CheckBoxList
{

    #region String Expression

    public static MvcHtmlString CheckBoxListItem(this HtmlHelper htmlHelper, string name, string value)
    {
        return CheckBoxListItem(htmlHelper, name, value, false, (object)null /* htmlAttributes */);
    }

    public static MvcHtmlString CheckBoxListItem(this HtmlHelper htmlHelper, string name, string value, bool isChecked)
    {
        return CheckBoxListItem(htmlHelper, name, value, isChecked, (object)null /* htmlAttributes */);
    }

    public static MvcHtmlString CheckBoxListItem(this HtmlHelper htmlHelper, string name, string value, bool isChecked, object htmlAttributes)
    {
        return CheckBoxListItem(htmlHelper, name, value, isChecked, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
    }

    public static MvcHtmlString CheckBoxListItem(this HtmlHelper htmlHelper, string name, string value, bool isChecked, IDictionary<string, object> htmlAttributes)
    {
        return CheckBoxListItemHelper(htmlHelper, null /* metadata */, name, value, isChecked, htmlAttributes);
    }

    #endregion

    #region Lambda Expression

    //List<string> overloads
    public static MvcHtmlString CheckBoxListItemFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> optionValue, Expression<Func<TModel, List<string>>> selectedValues)
    {
        return CheckBoxListItemFor(html, optionValue, selectedValues, null /* htmlAttributes */);
    }

    public static MvcHtmlString CheckBoxListItemFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> optionValue, Expression<Func<TModel, List<string>>> selectedValues, object htmlAttributes)
    {
        //Get the metadata from the Lambda expression passed from the model & view data dictionary
        ModelMetadata selectedValuesMetadata = ModelMetadata.FromLambdaExpression(selectedValues, html.ViewData);
        return CheckBoxListItemFor(html, optionValue, selectedValuesMetadata, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
    }

    //string[] overloads
    public static MvcHtmlString CheckBoxListItemFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> optionValue, Expression<Func<TModel, string[]>> selectedValues)
    {

        return CheckBoxListItemFor(html, optionValue, selectedValues, null /* htmlAttributes */);
    }

    public static MvcHtmlString CheckBoxListItemFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> optionValue, Expression<Func<TModel, string[]>> selectedValues, object htmlAttributes)
    {
        return CheckBoxListItemFor(html, optionValue, selectedValues, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
    }

    public static MvcHtmlString CheckBoxListItemFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> optionValue, Expression<Func<TModel, string[]>> selectedValues, IDictionary<string, object> htmlAttributes)
    {
        //Get the metadata from the Lambda expression passed from the model & view data dictionary
        ModelMetadata selectedValuesMetadata = ModelMetadata.FromLambdaExpression(selectedValues, html.ViewData);
        return CheckBoxListItemFor(html, optionValue, selectedValuesMetadata, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
    }

    private static MvcHtmlString CheckBoxListItemFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> optionValue, ModelMetadata metaData, IDictionary<string, object> htmlAttributes)
    {
        RouteValueDictionary attributes = htmlAttributes.ToRouteValueDictionary();

        if (optionValue == null)
        {
            throw new ArgumentNullException("expression");
        }

        //Get the checkbox name & value
        string name = metaData.PropertyName;
        string value = ModelMetadata.FromLambdaExpression(optionValue, html.ViewData).Model.ToString();


        //If the labelText is empty, return empty string
        if (string.IsNullOrEmpty(value))
        {
            return MvcHtmlString.Empty;
        }

        //Get selected items
        List<string> selections = (List<string>)metaData.Model;

        bool isChecked = false;
        //See if this item is checked
        if (selections.Contains(value))
        {
            isChecked = true;
        }

        return CheckBoxListItemHelper(html, metaData, name, value, isChecked, attributes);
    }
    #endregion

    private static MvcHtmlString CheckBoxListItemHelper(HtmlHelper htmlHelper, ModelMetadata metadata, string name, string value, bool isChecked, IDictionary<string, object> htmlAttributes)
    {
        string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
        //Begin building html
        TagBuilder tag = new TagBuilder("input");               // <input 
        tag.Attributes.Add("type", "checkbox");                 // type="checkbox"
        tag.Attributes.Add("name", fullName);                   // name={selectedValuesPropertyName}
        tag.Attributes.Add("value", value);                     // value="{value}"
        tag.Attributes.Add("id", "chk" + fullName + value);     // id="chk{selectedValuesPropertyName}{Value}"

        //See if this item is checked
        if (isChecked)
        {
            tag.Attributes.Add("checked", "checked");
        }

        tag.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata));
        tag.MergeAttributes(htmlAttributes); //Add attribut collection to element
        return MvcHtmlString.Create(tag.ToString(TagRenderMode.Normal)); //Render html
    }

}