能够按照 tagHelper 提供的方式添加条件 css 类。
此代码类似于 AnchorTagHelper asp-route-* 用于添加路由值的行为。
[HtmlTargetElement("div", Attributes = ClassPrefix + "*")]
public class ConditionClassTagHelper : TagHelper
{
private const string ClassPrefix = "condition-class-";
[HtmlAttributeName("class")]
public string CssClass { get; set; }
private IDictionary<string, bool> _classValues;
[HtmlAttributeName("", DictionaryAttributePrefix = ClassPrefix)]
public IDictionary<string, bool> ClassValues
{
get {
return _classValues ?? (_classValues =
new Dictionary<string, bool>(StringComparer.OrdinalIgnoreCase));
}
set{ _classValues = value; }
}
public override void Process(TagHelperContext context, TagHelperOutput output)
{
var items = _classValues.Where(e => e.Value).Select(e=>e.Key).ToList();
if (!string.IsNullOrEmpty(CssClass))
{
items.Insert(0, CssClass);
}
if (items.Any())
{
var classes = string.Join(" ", items.ToArray());
output.Attributes.Add("class", classes);
}
}
}
在 _ViewImports.cshtml 中添加对 taghelper 的引用,如下所示
@addTagHelper "*, WebApplication3"
在View中使用tagHelper:
<div condition-class-active="Model.Active" condition-class-show="Model.Display">
</div>
Active = true 和 Display = true 的结果是:
<div class="active show">
</div>