Question

I have an HtmlHelper extension method that looks like this:

public static MvcHtmlString TextBoxWithMaxLengthFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression, string name)
{
    return html.TextBoxFor(expression, new { maxlength = 50 });
}

I’d like to replace the 50 with the value of the StringLength data annotation on the given property, if one is defined. How do I go about getting at the property’s attributes?

Answer 1

Found the answer:

public static MvcHtmlString TextBoxWithMaxLengthFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression)
{
    var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
    var property = html.ViewData.Model.GetType().GetProperty(metadata.PropertyName);
    var attributes = property.GetCustomAttributes(typeof(StringLengthAttribute), true);
    var maxLength = attributes.Length > 0 ? ((StringLengthAttribute)attributes[0]).MaximumLength : 50;
    return html.TextBoxFor(expression, new { maxlength = maxLength });
}