Word forms provider

The IWordFormsProvider interface is designed to implement a word forms provider for searching by word forms. For information on searching by word forms, see Search for different word forms page.

The IWordFormsProvider interface contains only one GetWordForms method, which returns various forms for the word passed as an argument. An example implementation of a simple provider of word forms is presented below.


public class SimpleWordFormsProvider : IWordFormsProvider
    public string[] GetWordForms(string word)
        List<string> result = new List<string>();
        // We assume that the input word is in the plural, then we add the singular
        if (word.Length > 2 &&
            word.EndsWith("es", StringComparison.InvariantCultureIgnoreCase))
            result.Add(word.Substring(0, word.Length - 2));
        if (word.Length > 1 &&
            word.EndsWith("s", StringComparison.InvariantCultureIgnoreCase))
            result.Add(word.Substring(0, word.Length - 1));
        // Then we assume that the input word is in the singular, we add the plural
        if (word.Length > 1 &&
            word.EndsWith("e", StringComparison.InvariantCultureIgnoreCase))
            result.Add(word + "s");
        if (word.Length > 1 &&
            word.EndsWith("y", StringComparison.InvariantCultureIgnoreCase))
            result.Add(word.Substring(0, word.Length - 1) + "is");
        result.Add(word + "es");
        // All rules are implemented in the EnglishWordFormsProvider class
        return result.ToArray();

By default, the EnglishWordFormsProvider class is used, which for English generates various forms of nouns, adjectives, pronouns, verbs, etc. An example of setting a custom provider of word forms is presented below.


string indexFolder = @"c:\MyIndex\";
string documentsFolder = @"c:\MyDocuments\";
// Creating an index in the specified folder
Index index = new Index(indexFolder);
// Indexing documents from the specified folder
// Setting the custom word forms provider instance
index.Dictionaries.WordFormsProvider = new SimpleWordFormsProvider();
// Creating a search options instance
SearchOptions options = new SearchOptions();
options.UseWordFormsSearch = true; // Enabling search for word forms
// Searching in the index
SearchResult result = index.Search("relative", options);
// The following words can be found:
// relative
// relatives

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