Create CheckboxFor MVC helper with title attribute from model description

问题

I've created a text box helper to add a title (tooltip) taken from the description attribute for the field in a model:

 public static MvcHtmlString TextBoxForWithTitle<Tmodel, TProperty>(this HtmlHelper<Tmodel> htmlHelper, Expression<Func<Tmodel, TProperty>> expression, object htmlAttributes = null)
    {
        var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
        string textboxText = metaData.DisplayName ?? metaData.PropertyName ?? htmlFieldName.Split('.').Last();
        if (string.IsNullOrEmpty(textboxText))
            return MvcHtmlString.Empty;
        var textbox = new TagBuilder("input");
        textbox.MergeAttributes(new RouteValueDictionary(htmlAttributes));
        if (!string.IsNullOrEmpty(metaData.Description))
            textbox.Attributes.Add("title", metaData.Description);
        return MvcHtmlString.Create(textbox.ToString());
    }

I know the checkbox is also an 'input' type element but I have no idea how to construct a helper to use the description as a title.

 public static MvcHtmlString CheckBoxForWithTitle<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes = null)
    {
        var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
        string chkboxText = metaData.DisplayName ?? metaData.PropertyName ?? htmlFieldName.Split('.').Last();
        MemberExpression memberExpression = expression.Body as MemberExpression;
        string parameterName = memberExpression.Member.Name;

        if (string.IsNullOrEmpty(chkboxText))
            return MvcHtmlString.Empty;
        var chkbox = new MvcHtmlString(
            string.Format(
            "<input type=\"checkbox\" name=\"{0}\" id=\"{0}\" value=\"{1}\" {2} />",
            parameterName, 
        chkbox.MergeAttributes(new RouteValueDictionary(htmlAttributes));
        if (!string.IsNullOrEmpty(metaData.Description))
            chkbox.Attributes.Add("title", metaData.Description);
        return MvcHtmlString.Create(chkbox.ToString());
    }

回答1:

You current implementations are not taking into account model binding and ModelState, do not generate the attributes necessary for unobtrusive validation and can generate incorrect id attributes.

Make use of the existing html helper methods in your own helpers so you generate the correct html. Your TextBoxForWithTitle() method need only be

public static MvcHtmlString TextBoxForWithTitle<Tmodel, TProperty>(this HtmlHelper<Tmodel> htmlHelper, Expression<Func<Tmodel, TProperty>> expression, object htmlAttributes = null)
{
    var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
    IDictionary<string, object> attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
    if (!string.IsNullOrEmpty(metaData.Description))
    {
        attributes.Add("title", metaData.Description);
    }
    return htmlHelper.TextBoxFor(expression, attributes);
}

and similarly the CheckBoxForWithTitle() would be the same except

return htmlHelper.CheckBoxFor(expression, attributes);

Side note: To see how the existing helpers actually work, you can view the source code here

回答2:

I tried and it seems to work so far - still have to try a few examples where I need the ID of the element:

 public static MvcHtmlString CheckBoxForWithTitle<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes = null)
    {
        var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
        string chkboxText = metaData.DisplayName ?? metaData.PropertyName ?? htmlFieldName.Split('.').Last();
        MemberExpression memberExpression = expression.Body as MemberExpression;
        string parameterName = memberExpression.Member.Name;

        if (string.IsNullOrEmpty(chkboxText))
            return MvcHtmlString.Empty;
        var chkbox = new TagBuilder("input");
        chkbox.Attributes.Add("type", "checkbox");
        chkbox.MergeAttributes(new RouteValueDictionary(htmlAttributes));
        if (!string.IsNullOrEmpty(metaData.Description))
            chkbox.Attributes.Add("title", metaData.Description);
        return MvcHtmlString.Create(chkbox.ToString());
    }

来源：https://stackoverflow.com/questions/30127866/create-checkboxfor-mvc-helper-with-title-attribute-from-model-description