source: node_modules/prismjs/components/prism-aspnet.js

Prism.languages.aspnet = Prism.languages.extend('markup', {
        'page-directive': {
                pattern: /<%\s*@.*%>/,
                alias: 'tag',
                inside: {
                        'page-directive': {
                                pattern: /<%\s*@\s*(?:Assembly|Control|Implements|Import|Master(?:Type)?|OutputCache|Page|PreviousPageType|Reference|Register)?|%>/i,
                                alias: 'tag'
                        },
                        rest: Prism.languages.markup.tag.inside
                }
        },
        'directive': {
                pattern: /<%.*%>/,
                alias: 'tag',
                inside: {
                        'directive': {
                                pattern: /<%\s*?[$=%#:]{0,2}|%>/,
                                alias: 'tag'
                        },
                        rest: Prism.languages.csharp
                }
        }
});
// Regexp copied from prism-markup, with a negative look-ahead added
Prism.languages.aspnet.tag.pattern = /<(?!%)\/?[^\s>\/]+(?:\s+[^\s>\/=]+(?:=(?:("|')(?:\\[\s\S]|(?!\1)[^\\])*\1|[^\s'">=]+))?)*\s*\/?>/;

// match directives of attribute value foo="<% Bar %>"
Prism.languages.insertBefore('inside', 'punctuation', {
        'directive': Prism.languages.aspnet['directive']
}, Prism.languages.aspnet.tag.inside['attr-value']);

Prism.languages.insertBefore('aspnet', 'comment', {
        'asp-comment': {
                pattern: /<%--[\s\S]*?--%>/,
                alias: ['asp', 'comment']
        }
});

// script runat="server" contains csharp, not javascript
Prism.languages.insertBefore('aspnet', Prism.languages.javascript ? 'script' : 'tag', {
        'asp-script': {
                pattern: /(<script(?=.*runat=['"]?server\b)[^>]*>)[\s\S]*?(?=<\/script>)/i,
                lookbehind: true,
                alias: ['asp', 'script'],
                inside: Prism.languages.csharp || {}
        }
});