Search for text containing special characters Leave feedback

If a search query must contain special characters that are used as ordinary characters and not as query syntax elements, these characters must be escaped. The special characters are:

( ) : " & | ! ^ ~ * ? \ space

These characters can be escaped by adding a \ sign to the left of the character. For example:
\& - escaping & character;
\~ - escaping ~ character;
\s - escaping space character.
See Search operation table for details on search query syntax.

However, if the escaped character is a separator, it will still not be found in the text, since separators are not indexed. As a result, words containing such characters will also not be found when searching for an exact match.

If the search query contains separator characters, words containing these characters will not be found, because during indexing these characters break the word into parts and are not indexed themselves. Therefore, when performing a search, the query must be checked for the content of separator characters. Each word containing such characters should be broken into several smaller words and form a search phrase.

In the example below, the character types are set in the alphabet of a new index before documents are added. Since version 26.10, the alphabet can be changed only while the index contains no documents; otherwise, InvalidOperationException is thrown. For details, see the Alphabet page.

The order of processing each word in a search query is as follows:

1. If separators are present in the word, they are replaced by spaces, and the word search is converted to a phrase search.
2. If special characters are present in the word, they are escaped.

C#

string indexFolder = @"c:\MyIndex\";
string documentsFolder = @"c:\MyDocuments\";

// Creating a new index in the specified folder (the existing index files are deleted)
Index index = new Index(indexFolder, true);

// Setting character types before indexing documents
index.Dictionaries.Alphabet.SetRange(new char[] { '&' }, CharacterType.Letter);
index.Dictionaries.Alphabet.SetRange(new char[] { '-' }, CharacterType.Separator);

// Indexing documents from the specified folder
index.Add(documentsFolder);

// Defining a search query
string word = "rock&roll-music";

// Replacing separators with the space characters
StringBuilder result = new StringBuilder();
for (int i = 0; i < word.Length; i++)
{
    char character = word[i];
    CharacterType characterType = index.Dictionaries.Alphabet.GetCharacterType(character);
    if (characterType == CharacterType.Separator)
    {
        result.Append(' ');
    }
    else
    {
        result.Append(character);
    }
}

// Escaping special characters
const string specialCharacters = "():\"&|!^~*?\\";
for (int i = result.Length - 1; i >= 0; i--)
{
    char c = result[i];
    if (specialCharacters.Contains(c.ToString()))
    {
        result.Insert(i, '\\');
    }
}

string query = result.ToString();
if (query.Contains(" "))
{
    query = "\"" + query + "\"";
}

// Searching
SearchResult searchResult = index.Search(query);

You may easily run the code from documentation articles and see the features in action in our GitHub examples:

• GroupDocs.Search for .NET examples

• GroupDocs.Search for Java examples

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