我想使用Razor的特性，在属性值为null的情况下，不在标记内生成属性输出。所以当剃刀相遇时
public static MvcHtmlString WriteHeader(this HtmlHelper html, string s, int? hLevel = 1, object htmlAttributes = null)
{
if ((hLevel == null) ||
(hLevel < 1 || hLevel > 4) ||
(s.IsNullOrWhiteSpace()))
return new MvcHtmlString("");
string cssClass = null, cssId = null, cssStyle = null;
if (htmlAttributes != null)
{
var T = htmlAttributes.GetType();
var propInfo = T.GetProperty("class");
var o = propInfo.GetValue(htmlAttributes);
cssClass = o.ToString().IsNullOrWhiteSpace() ? null : o.ToString();
propInfo = T.GetProperty("id");
o = propInfo.GetValue(htmlAttributes);
cssId = o.ToString().IsNullOrWhiteSpace() ? null : o.ToString();
propInfo = T.GetProperty("style");
o = propInfo.GetValue(htmlAttributes);
cssStyle = o.ToString().IsNullOrWhiteSpace() ? null : o.ToString();
}
var hTag = new TagBuilder("h" + hLevel);
hTag.MergeAttribute("id", cssId);
hTag.MergeAttribute("class", cssClass);
hTag.MergeAttribute("style", cssStyle);
hTag.InnerHtml = s;
return new MvcHtmlString(hTag.ToString());
}
我发现，尽管“类”和“样式”属性为空值，TagBuilder仍然把它们作为空字符串，比如
我的问题是——这种行为真的应该发生吗？如何使用TagBuilder实现空值的缺席属性？
我在VS2013中尝试过这个，MVC5。
TagBuilder写入所有指定的属性，除了空的或空的“id”属性。以下是在内部使用类TagBuilder的代码：
private void AppendAttributes(StringBuilder sb)
{
foreach (var attribute in Attributes)
{
string key = attribute.Key;
if (String.Equals(key, "id", StringComparison.Ordinal /* case-sensitive */) && String.IsNullOrEmpty(attribute.Value))
{
continue; // DevDiv Bugs #227595: don't output empty IDs
}
string value = HttpUtility.HtmlAttributeEncode(attribute.Value);
sb.Append(' ')
.Append(key)
.Append("=\"")
.Append(value)
.Append('"');
}
}
您可以按如下方式创建Html扩展：
public static MvcHtmlString WriteHeader(this HtmlHelper html, string s, int? hLevel = 1, object htmlAttributes = null)
{
var hTag = new TagBuilder("h" + hLevel);
hTag.MergeAttributes(HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
hTag.InnerHtml = s;
return MvcHtmlString.Create(hTag.ToString());
}
并且，例如，可以如下使用：
@Html.WriteHeader("hello1", 1)
@Html.WriteHeader("hello2", 2, new { @class = string.Empty, style = string.Empty })
@Html.WriteHeader("hello3", 3, new { id = "id3", @class = "css3", style = "style3" })
生成以下HTML代码：
<h1>hello1</h1>
<h2 class="" style="">hello2</h2>
<h3 class="css3" id="id3" style="style3">hello3</h3>
