关于TagHelper的那些事情——自定义TagHelper(格式化输出、依赖注入使用)

    /// <summary>
    /// Class used to represent the output of an <see cref="ITagHelper"/>.
    /// </summary>
    public class TagHelperOutput
    {
        /// <summary>
        /// Instantiates a new instance of <see cref="TagHelperOutput"/>.
        /// </summary>
        /// <param name="tagName">The HTML element‘s tag name.</param>
        /// <param name="attributes">The HTML attributes.</param>
        public TagHelperOutput(string tagName, IDictionary<string, object> attributes)
        {
            ...
        }

        /// <summary>
        /// The HTML element‘s tag name.
        /// </summary>
        /// <remarks>
        /// A whitespace or <c>null</c> value results in no start or end tag being rendered.
        /// </remarks>
        public string TagName { get; set; }

        /// <summary>
        /// The HTML element‘s pre content.
        /// </summary>
        /// <remarks>Value is prepended to the <see cref="ITagHelper"/>‘s final output.</remarks>
        public TagHelperContent PreContent{ get; }

        /// <summary>
        /// The HTML element‘s main content.
        /// </summary>
        /// <remarks>Value occurs in the <see cref="ITagHelper"/>‘s final output after <see cref="PreContent"/> and
        /// before <see cref="PostContent"/></remarks>
        public TagHelperContent Content { get; }

        /// <summary>
        /// The HTML element‘s post content.
        /// </summary>
        /// <remarks>Value is appended to the <see cref="ITagHelper"/>‘s final output.</remarks>
        public TagHelperContent PostContent { get; }

        /// <summary>
        /// <c>true</c> if <see cref="Content"/> has been set, <c>false</c> otherwise.
        /// </summary>
        public bool IsContentModified { get; }

        /// <summary>
        /// Indicates whether or not the tag is self-closing.
        /// </summary>
        public bool SelfClosing { get; set; }

        /// <summary>
        /// The HTML element‘s attributes.
        /// </summary>
        /// <remarks>
        /// MVC will HTML encode <see cref="string"/> values when generating the start tag. It will not HTML encode
        /// a <c>Microsoft.AspNet.Mvc.Rendering.HtmlString</c> instance. MVC converts most other types to a
        /// <see cref="string"/>, then HTML encodes the result.
        /// </remarks>
        public IDictionary<string, object> Attributes { get; }

        /// <summary>
        /// Changes <see cref="TagHelperOutput"/> to generate nothing.
        /// </summary>
        /// <remarks>
        /// Sets <see cref="TagName"/> to <c>null</c>, and clears <see cref="PreContent"/>, <see cref="Content"/>,
        /// and <see cref="PostContent"/> to suppress output.
        /// </remarks>
        public void SuppressOutput()
        {
           ...
        }
    }

[Activate]
public ViewContext ViewContext { get; set; }