maxlength attribute of a text box from the DataAnnotations StringLength in Asp.Net MVC

Question

I am working on an MVC2 application and want to set the maxlength attributes of the text inputs.

I have already defined the stringlength attribute on the Model objec

Answer 1

I found Darin's reflection based approach to be especially helpful. I found that it was a little more reliable to use the metadata ContainerType as the basis to get the property info, as this method can get called within mvc editor/display templates (where TModel ends up being a simple type such as string).

public static MvcHtmlString CustomTextBoxFor<TModel, TProperty>(
    this HtmlHelper<TModel> htmlHelper, 
    Expression<Func<TModel, TProperty>> expression, 
    object htmlAttributes
)
{
    var metadata = ModelMetadata.FromLambdaExpression( expression, new ViewDataDictionary<TModel>( htmlHelper.ViewDataContainer.ViewData ) );
    var stringLength = metadata.ContainerType.GetProperty(metadata.PropertyName)
        .GetCustomAttributes(typeof(StringLengthAttribute), false)
        .FirstOrDefault() as StringLengthAttribute;

    var attributes = (IDictionary<string, object>)new RouteValueDictionary(htmlAttributes);
    if (stringLength != null)
    {
        attributes.Add("maxlength", stringLength.MaximumLength);
    }
    return htmlHelper.TextBoxFor(expression, attributes);
}