twenty eight twelve

CheckBoxList Helper extension method ASP.NET MVC 3

Here's a quick and dirty html helper for checkboxes in ASP.NET MVC 3. I'm sure Microsoft will eventually package one with the MVC framework just like they will a radiobuttonlist helper, but in the meantime, this one suits my purposes.

Of course, from a front-end point of view, a multi-select listbox is also an option, but checkboxes are a little more robust when it comes to user interaction. Nothing is more annoying as a user than forgetting to ctrl-click and having all your previous selections disappear.

You can probably find variations around, most that I've seen use a generic list of a custom class - mine uses a MultiSelectList instead, just for fun.

public static class NSCheckboxListExtensions
{
    public static MvcHtmlString CheckboxListFor<TModel, TProperty>(
                this HtmlHelper<TModel> htmlHelper,
                Expression<Func<TModel, TProperty>> expression,
                MultiSelectList listOfValues)
    {
        var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        var sb = new StringBuilder();

        if (listOfValues != null)
        {
            foreach (var item in listOfValues)
            {
                var id = string.Format("{0}_{1}", htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(ExpressionHelper.GetExpressionText(expression)), item.Value);
                var name = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(ExpressionHelper.GetExpressionText(expression));
                var label = htmlHelper.Label(id, HttpUtility.HtmlEncode(item.Text));

                var cb = new TagBuilder("input");
                cb.MergeAttribute("type", "checkbox");
                cb.MergeAttribute("name", name);
                cb.MergeAttribute("value", @item.Value);
                cb.MergeAttribute("id", id);
                if (@item.Selected)
                {
                    cb.MergeAttribute("checked", "checked");
                }
                sb.AppendFormat("{0}{1}</br>", cb, label);
            }
        }
        return MvcHtmlString.Create(sb.ToString());
    }
}