如何限制此HTML帮助程序方法的参数值？

Question

I made a html helper for the facebook like button.

public static MvcHtmlString FacebookLike(this HtmlHelper helper, bool send, bool showFaces, string layout, string href = null, int width = 450)
{
    var div = new TagBuilder("div");
    div.AddCssClass("fb-like");
    div.MergeAttribute("data-send", send.ToString());
    div.MergeAttribute("data-width", width.ToString());
    div.MergeAttribute("data-show-faces", showFaces.ToString());
    div.MergeAttribute("data-layout", layout);
    if (href != null)
    {
        div.MergeAttribute("data-href", href);
    }

    return new MvcHtmlString(div.ToString());
}

The layout parameter only has 3 possible values (standard, button_count and box_count). My question is how can I make this only accept those 3 values?

Thanks for any help you can give.

Answer 1

Make it an enum :

public enum LayoutType
{
    standard,
    button_count,
    box_count
}

and then change your method a bit:

public static MvcHtmlString FacebookLike(this HtmlHelper helper, bool send, bool showFaces, LayoutType layout, string href = null, int width = 450)
{
    var div = new TagBuilder("div");
    div.AddCssClass("fb-like");
    div.MergeAttribute("data-send", send.ToString());
    div.MergeAttribute("data-width", width.ToString());
    div.MergeAttribute("data-show-faces", showFaces.ToString());
    div.MergeAttribute("data-layout", Enum.GetName(typeof(LayoutType), layout));
    if (href != null)
    {
        div.MergeAttribute("data-href", href);
    }

    return new MvcHtmlString(div.ToString());
}

note the signature now uses the enum and the data-layout is set by grabbing the name of the enum passed in.