Session: Querying: How to use Highlighting

Highlighting can be a great feature for increasing search UX. To take leverage of it use Highlight method.

Syntax

IRavenQueryable<T> Highlight(
    string fieldName,
    int fragmentLength,
    int fragmentCount,
    out Highlightings highlightings);

IRavenQueryable<T> Highlight(
    string fieldName,
    int fragmentLength,
    int fragmentCount,
    HighlightingOptions options,
    out Highlightings highlightings);

IRavenQueryable<T> Highlight(
    Expression<Func<T, object>> path,
    int fragmentLength,
    int fragmentCount,
    out Highlightings highlightings);

IRavenQueryable<T> Highlight(
    Expression<Func<T, object>> path,
    int fragmentLength,
    int fragmentCount,
    HighlightingOptions options,
    out Highlightings highlightings);

Options

public string GroupKey { get; set; }

public string[] PreTags { get; set; }

public string[] PostTags { get; set; }

Example

List<SearchItem> results = session
    .Query<SearchItem, ContentSearchIndex>()
    .Highlight(x => x.Text, 128, 1, out Highlightings highlightings)
    .Search(x => x.Text, "raven")
    .ToList();

StringBuilder builder = new StringBuilder()
    .AppendLine("<ul>");

foreach (SearchItem result in results)
{
    string[] fragments = highlightings.GetFragments(result.Id);
    builder.AppendLine($"<li>{fragments.First()}</li>");
}

string ul = builder
    .AppendLine("</ul>")
    .ToString();

List<SearchItem> results = await asyncSession
    .Query<SearchItem, ContentSearchIndex>()
    .Highlight(x => x.Text, 128, 1, out Highlightings highlightings)
    .Search(x => x.Text, "raven")
    .ToListAsync();

StringBuilder builder = new StringBuilder()
    .AppendLine("<ul>");

foreach (SearchItem result in results)
{
    string[] fragments = highlightings.GetFragments(result.Id);
    builder.AppendLine($"<li>{fragments.First()}</li>");
}

string ul = builder
    .AppendLine("</ul>")
    .ToString();

from index 'ContentSearchIndex'
where search(Text, 'raven')
include highlight(Text, 128, 1)

Remarks