Passing checkbox selection through to an action

Question

I have a bunch of checkboxes that are used for the user to specify which columns they want to see on a grid:

Answer 1

The Html.CheckBox method has a strange implementation. Checkboxes will have a unique name, and essentially a true/false value. This is so that the value will easily map to a bool parameter in an Action.

As you have obviously noticed, this makes for a tricky situation when your checkboxes are dynamic.

The solution is to generate your own checkboxes, all using a common name and having unique values. These will map very nicely into your Action!

See this question too, for some great examples and explanations.

Here's the desired Action:

public ActionResult SetSelectedColumns(string[] selectedColumns) {
    // selectedColumns will contain the keys of all the checked columns.
}

And here's how to get your HTML to map correctly:

I highly recommend putting this functionality into an extension method, so that you can also incorporate ModelState and htmlAttributes. Here's my untested attempt:

    public static HtmlString CheckBoxAlt(this HtmlHelper html, string name, string value, bool selected, object htmlAttributes)
    {
        var tag = new TagBuilder("input");
        if (htmlAttributes != null)
            tag.MergeAttributes(new RouteValueDictionary(htmlAttributes));
        tag.MergeAttribute("type", "checkbox");
        tag.MergeAttribute("name", name);
        tag.MergeAttribute("value", value);
        // Determine if this check should be selected:
        var state = html.ViewData.ModelState[name];
        if (state != null)
        {
            var values = (string[])state.Value.ConvertTo(typeof(string[]));
            selected = Array.IndexOf(values, value) != -1;
        }
        if (selected)
            tag.MergeAttribute("checked", "checked");

        return new HtmlString(tag.ToString(TagRenderMode.SelfClosing));
    }