Is it possible to access additional metadata info from a custom display or editor template?

Question

I am aware that in a custom display or editor template I can get metadata about the model via ViewData.ModelMetadata, which has properties that indicate whether

Answer 1

Sure. First you'll need your attribute which implements IMetadataAware so that DataAnnotationsModelMetadataProvider knows about it

public class TooltipAttribute : Attribute, IMetadataAware {
    public TooltipAttribute(string tooltip) {
        this.Tooltip = tooltip;
    }

    public string Tooltip { get; set; }

    public void OnMetadataCreated(ModelMetadata metadata) {
        metadata.AdditionalValues["Tooltip"] = this.Tooltip;
    }
}

You can then access the attribute by creating a helper method:

public static IHtmlString TooltipFor<TModel, TValue>(
                             this HtmlHelper<TModel> html,
                             Expression<Func<TModel, TValue>> expression) {
    var data = ModelMetadata.FromLambdaExpression<TModel, TValue>(expression, html.ViewData);
    if (data.AdditionalValues.ContainsKey("Tooltip"))
        return new HtmlString((string)data.AdditionalValues["Tooltip"]);

    return new HtmlString("");
}