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

// Make a full-text search dynamic query:
// ======================================
List<Employee> employeesResults = session
   // Make a dynamic query on 'Employees' collection
  .Query<Employee>()
   // Search for documents containing the term 'sales' in their 'Notes' field
  .Search(x => x.Notes, "sales")
   // Request to highlight the searched term by calling 'Highlight'
  .Highlight(
      x => x.Notes, // The document-field name in which we search
      35,           // Max length of each text fragment
      4,            // Max number of fragments to return per document
      out Highlightings salesHighlights) // An out param for getting the highlighted text fragments
   // Execute the query
  .ToList();

Parameters
fieldName	string	Name of a field to highlight.
path	`Expression<Func<T, object>>`	Path to a field to highlight.
fragmentLength	int	Maximum length of text fragments that will be returned.
fragmentCount	int	Maximum number of fragments that will be returned.
options	`HighlightingOptions`	Options that can be used for customization.
highlightings	`Highlightings`	Instance of a Highlightings that contains the highlight fragments for each returned result.

Options

public string GroupKey { get; set; }

public string[] PreTags { get; set; }

public string[] PostTags { get; set; }

Options
GroupKey	string	Grouping key for the results. If `null` results are grouped by document ID (default).
PreTags	`string[]`	Array of pre tags used when highlighting.
PostTags	`string[]`	Array of post tags used when highlighting.

Example

Sync
Async
RQL

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

Note

Default  tags are coloured and colours are returned in following order:

yellow,
lawngreen,
aquamarine,
magenta,
palegreen,
coral,
wheat,
khaki,
lime,
deepskyblue,
deeppink,
salmon,
peachpuff,
violet,
mediumpurple,
palegoldenrod,
darkkhaki,
springgreen,
turquoise,
powderblue

Syntax​

Options​

Example​

Remarks​

Syntax

Options

Example

Remarks