MVC EditorFor 自定义助手

Question

我正在尝试为 EditorFor 创建一个自定义助手。我想从模型中获取字符串长度并将其添加到 html 属性中。

到目前为止，我有以下内容，但这并不适用于添加的新属性。

    public static IHtmlString MyEditorFor<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression, object ViewData, bool disabled = false, bool visible = true)
    {
        var member = expression.Body as MemberExpression;
        var stringLength = member.Member.GetCustomAttributes(typeof(StringLengthAttribute), false).FirstOrDefault() as StringLengthAttribute;

        RouteValueDictionary viewData =  HtmlHelper.AnonymousObjectToHtmlAttributes(ViewData);
        RouteValueDictionary htmlAttributes = HtmlHelper.AnonymousObjectToHtmlAttributes(viewData["htmlAttributes"]);

        if (stringLength != null)
        {
            htmlAttributes.Add("maxlength", stringLength.MaximumLength);
        }

        return htmlHelper.EditorFor(expression, ViewData);
    }

Answer 1

您在方法参数中返回原始 ViewData 属性，而不是 return htmlHelper.EditorFor(expression, ViewData) 上的自定义 HTML 属性集合。基于this answer，您的返回方法应更改为：

public static IHtmlString MyEditorFor<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression, object ViewData, bool disabled = false, bool visible = true)
{
    var member = expression.Body as MemberExpression;
    var stringLength = member.Member.GetCustomAttributes(typeof(StringLengthAttribute), false).FirstOrDefault() as StringLengthAttribute;

    RouteValueDictionary viewData =  HtmlHelper.AnonymousObjectToHtmlAttributes(ViewData);
    RouteValueDictionary htmlAttributes = HtmlHelper.AnonymousObjectToHtmlAttributes(viewData["htmlAttributes"]);

    if (stringLength != null)
    {
        htmlAttributes.Add("maxlength", stringLength.MaximumLength);
    }

    return htmlHelper.EditorFor(expression, htmlAttributes); // use custom HTML attributes here
}

然后，像这样在视图端应用自定义 HTML 帮助器：

@Html.MyEditorFor(model => model.Property, new { htmlAttributes = new { @maxlength = "10" }})

编辑：

此方法适用于 MVC 5 (5.1) 及更高版本，我不确定它是否适用于早期版本（请参阅此问题：Html attributes for EditorFor() in ASP.NET MVC）。

对于早期的 MVC 版本，更倾向于使用HtmlHelper.TextBoxFor，它当然具有maxlength 属性：

return htmlHelper.TextBoxFor(expression, htmlAttributes);

其他参考资料：

Set the class attribute to Html.EditorFor in ASP.NET MVC Razor View

HTML.EditorFor adding class not working