如何向我的自定义 HtmlHelper 添加验证消息？

Question

我有一个使用数据注释的类：

[Required(ErrorMessage = "You must indicate which sex you are.)]
public string Sex { get; set; }

我还创建了一个名为 RadioButtonListFor 的自定义 HtmlHelper，我可以这样调用它：

@Html.RadioButtonListFor(m => m.Sex, "SexList")

我的 SexList 定义如下：

IList<string> SexList = new List() { "Male", "Female"};

下面是 RadioButtonListFor 扩展（尚未完全完成）：

public static class RadioButtonListForExtentions
{
    public static IHtmlString RadioButtonListFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, string list)
    {
        string prefix = ExpressionHelper.GetExpressionText(expression);
        if (string.IsNullOrEmpty(prefix))
            prefix = "empty";
        int index = 0;

        var items = helper.ViewData.Eval(list) as IEnumerable;
        if (items == null)
            throw new NullReferenceException("Cannot find " + list + "in view data");

        string txt = string.Empty;
        foreach (var item in items)
        {
            string id = string.Format("{0}_{1}", prefix, index++).Replace('.','_');
            TagBuilder tag = new TagBuilder("input"); 
            tag.MergeAttribute("type", "radio");
            tag.MergeAttribute("name", prefix);
            tag.MergeAttribute("id", id);
            tag.MergeAttribute("data-val-required", "Missing");
            tag.MergeAttribute("data-val", "true");

            txt += tag.ToString(TagRenderMode.Normal);
            txt += item;
        }

        return helper.Raw(txt);
    }
}

我的问题是这样的：现在我已经在属性“data-val-required”中硬编码了“Missing”这个词。如何获取我在数据注释中所述的文本？

Answer 1

啊...在睡个好觉后我自己找到了解决方案:-)

用以下内容替换 RadioButtonListFor：

public static IHtmlString RadioButtonListFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, string list)
    {
        string prefix = ExpressionHelper.GetExpressionText(expression);
        if (string.IsNullOrEmpty(prefix))
            prefix = "empty";
        int index = 0;

        var items = helper.ViewData.Eval(list) as IEnumerable;
        if (items == null)
            throw new NullReferenceException("Cannot find " + list + "in view data");

        var validationAttributes = helper.GetUnobtrusiveValidationAttributes(prefix);

        string txt = string.Empty;
        foreach (var item in items)
        {
            string id = string.Format("{0}_{1}", prefix, index++).Replace('.','_');
            TagBuilder tag = new TagBuilder("input"); 
            tag.MergeAttribute("type", "radio");
            tag.MergeAttribute("name", prefix);
            tag.MergeAttribute("id", id);
            foreach (KeyValuePair<string, object> pair in validationAttributes)
            {
                tag.MergeAttribute(pair.Key, pair.Value.ToString());
            }
            txt += tag.ToString(TagRenderMode.Normal);
            txt += item;
        }

        return helper.Raw(txt);
    }

基本上我添加了“validationAttributes”，它显然是我的验证项的字典。循环遍历这些并添加它们使其工作起来就像一个魅力！

2011 年 10 月 13 日编辑：

最终得到以下解决方案。我决定发送一个字典，其中键是单选按钮值，字典的值是单选按钮文本，而不是仅仅获取字符串列表。

public static IHtmlString RadioButtonListFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, string list)
    {
        string prefix = ExpressionHelper.GetExpressionText(expression);
        if (string.IsNullOrEmpty(prefix))
            prefix = "empty";

        // find existing value - if any
        string value = helper.ViewData.Eval(prefix) as string;

        var validationAttributes = helper.GetUnobtrusiveValidationAttributes(prefix);
        string txt = string.Empty;

        // create hidden field for error msg/value
        TagBuilder tagHidden = new TagBuilder("input");
        tagHidden.MergeAttribute("type", "hidden");
        tagHidden.MergeAttribute("name", prefix);
        tagHidden.MergeAttribute("value", value);
        tagHidden.MergeAttribute("id", prefix.Replace('.', '_'));
        foreach (KeyValuePair<string, object> pair in validationAttributes)
        {
            tagHidden.MergeAttribute(pair.Key, pair.Value.ToString());
        }
        txt += tagHidden.ToString(TagRenderMode.Normal);

        // prepare to loop through items
        int index = 0;
        var items = helper.ViewData.Eval(list) as IDictionary<string, string>;
        if (items == null)
            throw new NullReferenceException("Cannot find " + list + "in view data");

        // create a radiobutton for each item. "Items" is a dictionary where the key contains the radiobutton value and the value contains the Radiobutton text/label
        foreach (var item in items)
        {
            string id = string.Format("{0}_{1}", prefix, index++).Replace('.','_');
            TagBuilder tag = new TagBuilder("input"); 
            tag.MergeAttribute("type", "radio");
            tag.MergeAttribute("name", prefix);
            tag.MergeAttribute("id", id);
            tag.MergeAttribute("value", item.Key);
            if (item.Key == value)
                tag.MergeAttribute("checked", "true");
            tag.MergeAttribute("onclick", "javascript:" + tagHidden.Attributes["id"] + ".value='" + item.Key + "'");
            txt += tag.ToString(TagRenderMode.Normal);
            txt += item.Value;
        }

        return helper.Raw(txt);
    }