Not able to get correct boolean value from SelectListItem in custom Radio Button

Question

I'm creating a custom radio button helper using tagbuilder. I'm making use of the steps suggested in the post: Custom helper for generating html tags for radio button and associated label , but have tweaked it a bit to pass the values to the radio button using List , somewhat like this:-

@{
    List<SelectListItem> inventory = new List<SelectListItem>();
    inventory.Add(new SelectListItem { Text = "True", Value = bool.TrueString, Selected = true });
    inventory.Add(new SelectListItem { Text = "False", Value = bool.FalseString});
}

But, even when I select true, it always takes the value as FALSE. Below, is my code for constructing tag builder, please let me know where I'm going wrong:

public static MvcHtmlString CustomRadioButtonFor<TModel>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, bool>> expression, IEnumerable<SelectListItem> radioList)
        {
            StringBuilder radiobutton = new StringBuilder();
            TagBuilder radio = null;
            TagBuilder label = null;

            string[] propertyNameParts = expression.Body.ToString().Split('.');
            string propertyName = propertyNameParts.Last();
            string booleanStr = "";

            // get the value of the property
            Func<TModel, bool> compiled = expression.Compile();
            var name = ExpressionHelper.GetExpressionText(expression);
            var metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
            if (metadata.Model != null)
            {

                booleanStr = Convert.ToString(compiled(htmlHelper.ViewData.Model));

            }
            else
                booleanStr = string.Empty;

            // convert it to a boolean
            bool isChecked = false;
            Boolean.TryParse(booleanStr, out isChecked);

            foreach (SelectListItem item in radioList)
            {
                radio = new TagBuilder("input");
                label = new TagBuilder("label");
                label.InnerHtml = item.Text;
                radio.Attributes.Add("type", "radio");
                radio.Attributes.Add("name", name);
                radio.Attributes.Add("value", booleanStr);
                radiobutton.Append(label.ToString());
                radiobutton.Append(radio.ToString());
            }
            return MvcHtmlString.Create(radiobutton.ToString());
        }

Any help would be appreciated. Thanks in advance!