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How to: Implement a Full-Text Search

This example shows you how to create full-text queries against plain character-based data in SQL Server tables. Full-text queries can include words and phrases, or multiple forms of a word or phrase.

 

What Is a Full-Text Search?

A full-text search allows fast and flexible indexing for keyword-based query of text data stored in a Microsoft SQL Server database. In contrast to the LIKE predicate, which only works on character patterns, full-text queries perform linguistic searches against this data, by operating on words and phrases based on rules of a particular language.

 

Implementing a Full-Text Search

To implement a full-text search, do the following.

  • Install the Full-Text Search sub-component of MS SQL. For detailed information on how to create a Full-Text Search on a database, see Full-Text Search.
  • Create a custom function operator by implementing the ICustomFunctionOperatorFormattable interface.

    
    using System.Data;
    using DevExpress.Xpo.DB;
    using DevExpress.Data.Filtering;
    
    public class FullTextContainsFunction : ICustomFunctionOperatorFormattable {
        #region ICustomFunctionOperator Members
        // Evaluates the function on the client
        public object Evaluate(params object[] operands) {
            // Full text search is not available on the client and should not be used there
            throw new NotImplementedException();
        }
        public string Name {
            get { return "FullTextContains"; }
        }
        public Type ResultType(params Type[] operands) {
            return typeof(bool);
        }
        #endregion
        #region ICustomFunctionOperatorFormattable Members
        // The function's expression to be evaluated on the server
        public string Format(Type providerType, params string[] operands) {
            // This example implements the function for MS SQL databases only
            if (providerType == typeof(MSSqlConnectionProvider))
                return string.Format("contains({0}, {1})", operands[0], operands[1]);
            throw new NotSupportedException(string.Concat("This provider is not supported: ", 
                providerType.Name));
        }
        #endregion
    }
    

 

Using a Full-Text Search (a simple search)

To use a custom function operator in criteria you should first register it via the CriteriaOperator.RegisterCustomFunction method.


using DevExpress.Data.Filtering;

public class Program {
    //...
    public static void Main(string[] arguments) {
        CriteriaOperator.RegisterCustomFunction(new FullTextContainsFunction());
        //...
    }
}

After registering the custom operator, you can use it in your criteria.


private void Form1_Load(object sender, EventArgs e) {
    xpCollection1.Criteria = CriteriaOperator.Parse("FullTextContains(ProjectName, 'Business')");
}

Querying_FullTextSearch

See Also