Add Attribute To Custom HtmlHelper's Elements

Question

I'm using this code to generate custom DropDownListFor

public static MvcHtmlString LookupFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression)
{
    ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
    string lookup = metadata.PropertyName;

    IEnumerable<lookup> list = Get(lookup);
    IEnumerable<SelectListItem> items = list.Select(o => new SelectListItem
                 {
                     Text = o.title,
                     Value = o.id.ToString(),
                     Selected = o.id.Equals(metadata.Model)
                 }).ToList();

    string id = "_" + (new Random()).Next(10000);
    MvcHtmlString dropDown = htmlHelper.DropDownListFor(expression, items, "---", new {title = lookup, id});
    return dropDown;
}

is it possible to add HTML attribute to some options ?

Simon Whitehead · Accepted Answer · 2012-08-15 22:16:51Z

2

You need to prefix class with @, because class is a keyword in C#:

MvcHtmlString dropDown = htmlHelper.DropDownListFor(expression, items, "---", new { @class = "cssClass", title = lookup, id});

answered Aug 15, 2012 at 22:16

Simon Whitehead

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1 Comment

Mironline Over a year ago

@Thank you simon , you right but my question is about accessing to option elements in this code.

2 revs · Accepted Answer · 2012-11-11 08:56:02Z

I found solution for this purpose

public static HtmlString LookupFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression)
        {
            ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
            string lookup = metadata.PropertyName;

            IEnumerable<lookup> list = Get(lookup).ToList();
            IEnumerable<SelectListItem> items = list.Select(o => new SelectListItem
            {
                Text = o.title,
                Value = o.id.ToString(),
                Selected = o.id.Equals(metadata.Model)
            }).ToList();

            string id = "_" + (new Random()).Next(10000);
            MvcHtmlString dropDown = htmlHelper.DropDownListFor(expression, items, "---", new { title = lookup, id });

            var xml = XDocument.Parse(dropDown.ToHtmlString());
            var xml_select = xml.Element("select");
            if (xml_select != null)
            {
                var options = xml_select.Elements("option");
                foreach(var c in options )
                {
                    var val_attribute = c.Attribute("value");
                    if (val_attribute != null)
                    {
                        string value = val_attribute.Value;
                        int tmp;
                        if (Int32.TryParse(value,out tmp))
                        {
                            var fd = list.FirstOrDefault(o => o.id == Convert.ToInt32(value));
                            if (fd == null) continue;
                            if (!fd.active)
                            {
                                c.SetAttributeValue("class", "deactive-lookup");
                            }
                        }
                    }
                }
            }
            string html_string;
            using (var stringWriter = new StringWriter())
            {
                using (var xmlTextWriter = XmlWriter.Create(stringWriter))
                {
                    xml.WriteTo(xmlTextWriter);
                    xmlTextWriter.Flush();
                    html_string =  stringWriter.GetStringBuilder().ToString();
                }
            }
            return  new HtmlString(html_string);
        }

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