MVC中My97date无法进行ValidationMessage修改

public static MvcHtmlString CalendarFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper,
    Expression<Func<TModel, TProperty>> expression)
        {
            TagBuilder tagBuilder = new TagBuilder("input");
            ModelMetadata metadata = ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, htmlHelper.ViewData);
            string name = ExpressionHelper.GetExpressionText(expression);
            htmlHelper.ValidateFor(expression);
            tagBuilder.MergeAttribute("name", name);
            tagBuilder.GenerateId(name);
            tagBuilder.MergeAttribute("type", "text");
            //核心代码，直接通过这个方法可以获取属性上的验证信息，如：“data-val= ....”。
            var vas = htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata);
            //string类型，看有没长度限制，如果有，增加maxlength，minlength
            if (metadata.ModelType == typeof(string))
            {
                var len = metadata.ContainerType.GetProperty(name).GetCustomAttribute(typeof(StringLengthAttribute));
                if (len != null)
                {
                    var stringlength = (StringLengthAttribute)len;
                    if (stringlength.MaximumLength > 0)
                    {
                        tagBuilder.MergeAttribute("maxlength", stringlength.MaximumLength.ToString());
                    }
                    if (stringlength.MinimumLength > 0)
                    {
                        tagBuilder.MergeAttribute("minlength", stringlength.MinimumLength.ToString());
                    }
                }
            }
            //如果model值不为，null，进行赋值。
            if (metadata.Model != null)
            {
                tagBuilder.MergeAttribute("value", metadata.Model.ToString());
            }
            tagBuilder.MergeAttributes(vas);
            tagBuilder.MergeAttribute("class", "Wdate");
            tagBuilder.MergeAttribute("onclick", "WdatePicker({el:‘" + name + "‘})");

            return new MvcHtmlString(tagBuilder.ToString());
        }