SQLiteCollationFunction Class

In This Topic

Base class for user-defined collation functions.

Syntax

Visual Basic
C#

'Declaration
 
Public MustInherit Class SQLiteCollationFunction 
   Inherits SQLiteFunction
   Implements System.IDisposable

public abstract class SQLiteCollationFunction : SQLiteFunction, System.IDisposable

Remarks

Use this class to derive classes for user-defined collation functions from it.

Collation functions are used for sorting. You should implement the comparison operation for it.

To register the user-defined collation funtion, create the class, derived from SQLiteCollationFunction and pass its name to the base class constructor.

You should also override Compare method. This method should implement the comparison operation.

Example

Example of the user-defined collation function which implements the string comparison.

csharp

public class MyCollation : SQLiteCollationFunction {

        public MyCollation() : base("StringCollation") { }

        protected override int Compare(string param1, string param2, SQLiteConnection connection) {

                return string.Compare(param1, param2);
        }
}

...

SQLiteConnection sqLiteConnection = new SQLiteConnection(@"Data Source=D:\SQLite\test.db");
      sqLiteConnection.Open();
MyCollation collation = new MyCollation();
      sqLiteConnection.RegisterFunction(collation);
SQLiteCommand command = new SQLiteCommand("select * from Dept order by DName collate StringCollation", sqLiteConnection);
      using (SQLiteDataReader rd = command.ExecuteReader()) {
while (rd.Read()) {
        long deptno = rd.GetInt64(0);
        string dname = rd.GetString(1);
        string loc = rd.GetString(2);
}
      }
      sqLiteConnection.UnRegisterFunction(collation);
      sqLiteConnection.Close();

Inheritance Hierarchy

System.Object
Devart.Data.SQLite.SQLiteFunction
Devart.Data.SQLite.SQLiteCollationFunction

Reference

SQLiteCollationFunction Members
Devart.Data.SQLite Namespace

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