public IActionResult Test() => View();

@{
    Layout = null;
}

<stars-block title-id="56" score="6" default="true"></stars-block>

public class StarsBlockTagHelper : TagHelper
{
    public int TitleId { get; set; }
    public int Score { get; set; }
    public bool Default { get; set; }

    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
        output.TagName = "div";
        output.Attributes.Add("class", "block-stars");
        output.Attributes.Add("data-title_id", TitleId);
        output.Attributes.Add("data-score", Score);
        output.Attributes.Add("data-default", Default);

        TagBuilder ul = new TagBuilder("ul");
        ul.AddCssClass("w3l-ratings");

        TagBuilder li;
        for (int i = 1; i <= 10; i =+ 2)
        {
            li = new TagBuilder("li");
            li.InnerHtml.AppendHtml(getStarHalf("left", i));
            li.InnerHtml.AppendHtml(getStarHalf("right", i + 1));

            ul.InnerHtml.AppendHtml(li);
        }

        output.Content.AppendHtml(ul);
    }

    private TagBuilder getStarHalf(string direction, int id)
    {
        TagBuilder div = new TagBuilder("div");
        div.AddCssClass("star-half");
        div.Attributes.Add("data-star_half_id", id.ToString());

        TagBuilder svg = new TagBuilder("svg");
        svg.Attributes.Add("version", "1.1");
        svg.Attributes.Add("id", "Layer_1");
        svg.Attributes.Add("xmlns", "http://www.w3.org/2000/svg");
        svg.Attributes.Add("xmlns:xlink", "http://www.w3.org/1999/xlink");
        svg.Attributes.Add("x", "0px");
        svg.Attributes.Add("y", "0px");
        svg.Attributes.Add("viewBox", "0 0 8.7 16.7");
        svg.Attributes.Add("xml:space", "preserve");

        TagBuilder path = new TagBuilder("path");
        path.TagRenderMode = TagRenderMode.SelfClosing;
        path.AddCssClass("star-half-" + direction);
        path.Attributes.Add("d", "M8.9,1.7L6,6.1L0.5,6.9l3.9,3.8l-0.9,5.5c1.8-1,3.6-1.9,5.4-2.9");

        svg.InnerHtml.AppendHtml(path);
        div.InnerHtml.AppendHtml(svg);

        return div;
    }

<div class="block-stars" data-title_id="56" data-score="6" default="true">
    <ul class="w3l-ratings" >
        <li>
            <div class="star-half" data-star_half_id="1">
                <svg
                 version="1.1"
                 id="Layer_1"
                 xmlns="http://www.w3.org/2000/svg"
                 xmlns:xlink="http://www.w3.org/1999/xlink"
                 x="0px"
                 y="0px"
                 viewBox="0 0 8.7 16.7"
                 xml:space="preserve">

                    <path class="star-half-left"
                          d="M8.9,1.7L6,6.1L0.5,6.9l3.9,3.8l-0.9,5.5c1.8-1,3.6-1.9,5.4-2.9"/>
                </svg>
            </div>
            <div class="star-half" data-star_half_id="2">
                <svg
                version="1.1"
                id="Layer_1"
                xmlns="http://www.w3.org/2000/svg"
                xmlns:xlink="http://www.w3.org/1999/xlink"
                x="0px"
                y="0px"
                viewBox="0 0 8.7 16.7"
                    xml:space="preserve">
                    <path class="star-half-right"
                          d="M8.9,1.7L6,6.1L0.5,6.9l3.9,3.8l-0.9,5.5c1.8-1,3.6-1.9,5.4-2.9"/>
                </svg>
            </div>
        </li>
        <!-- and so on 10 times -->
    </ul>
</div>