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Question:

In asp.net mvc I always see the built in html helpers they always have object htmlAttirbutes.

Then I usually do new {@id = "test", @class="myClass"}.

How do I extract a parameter like this in my own html helpers?

Like I am using "HtmlTextWriterTag" is their a way I can pass this whole object to the writer and it figured it out or what?

Also how does this work with big html helpers?

Like I am making a html helper and it uses all these tags.

Table
thead
tfooter
tbody
tr
td
a
img

Does that mean I have to make a html Attribute for each of these tags?


Best Answer:


I use a mix of both methods (Chtiwi Malek and rrejc) proposed earlier and it works great.

With this method, it will convert data_id to data-id. It will also overwrite default attribute values you have set earlier.

using System.ComponentModel;
...
public static MvcHtmlString RequiredLabelFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, object htmlAttributes)
{
    var metaData = ModelMetadata.FromLambdaExpression(expression, helper.ViewData);
    string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
    string labelText = metaData.DisplayName ?? metaData.PropertyName ?? htmlFieldName.Split('.').Last();
    if (String.IsNullOrEmpty(labelText))
        return MvcHtmlString.Empty;
    var label = new TagBuilder("label");
    label.Attributes.Add("for", helper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(htmlFieldName));
    foreach (PropertyDescriptor prop in TypeDescriptor.GetProperties(htmlAttributes))
    {
        // By adding the 'true' as the third parameter, you can overwrite whatever default attribute you have set earlier.
        label.MergeAttribute(prop.Name.Replace('_', '-'), prop.GetValue(htmlAttributes).ToString(), true);
    }
    label.InnerHtml = labelText;
    return MvcHtmlString.Create(label.ToString());
}

Note the comment about overwriting an attribute that has a default value in your code in the foreach.




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