TextFragment

Reports document.fragmentDirective. A false doesn't make your links unusable - they just load the page without scrolling - so this is a 'will the highlight happen' check, not a gate on generating them.

@inject Bit.Butil.TextFragment textFragment

var supported = await textFragment.IsSupported();

Only Start is required. Start plus End matches a whole range - the way to link to a paragraph without putting it all in the URL. Prefix and Suffix disambiguate without being highlighted themselves: they say what must sit either side of the match. Matching ignores case, collapses whitespace and only ever matches visible text.

var url = await textFragment.BuildUrl("/text-fragment",
    new TextFragmentDirective { Start = "fragment directive" });

// a range:
new TextFragmentDirective { Start = "Only Start", End = "visible text." }

Select some text on this page and press the button - this is the same feature as the browser's own 'Copy link to highlight'. A short selection becomes an exact match; a long one becomes a start/end range, so the URL stays a reasonable length without matching any less precisely.

@inject Bit.Butil.Clipboard clipboard
@inject Bit.Butil.Location location
@inject Bit.Butil.TextFragment textFragment

<button @onclick="CopyLink">Copy a link to the selection</button>

@code {
    private async Task CopyLink()
    {
        var directive = await textFragment.FromSelection();
        if (directive is null) return; // nothing selected

        var currentUrl = await location.GetHref();
        var url = await textFragment.BuildUrl(currentUrl, directive);
        await clipboard.WriteText(url);
    }
}

A text directive is only acted on as part of a navigation - there is no scripted 'scroll to this text'. This is a real navigation, so in a Blazor app it means a full reload unless the URL is the current page with a different fragment.

var url = await textFragment.BuildUrl("/text-fragment",
    new TextFragmentDirective { Start = "Style the highlight" });

await textFragment.Navigate(url);

Reads the directives back out of a URL - the inverse of BuildUrl. It takes a URL rather than reading the current one because the browser strips the directive off while navigating, so the page you are on no longer carries it. Parse a link before following it: to show what it will highlight, to rewrite it, or to expand the collapsed section that contains the phrase.

var directives = await textFragment.Parse(url);
if (directives.Length > 0) ExpandSectionContaining(directives[0].Start);