SQLiteScalarFunction Class

In This Topic

Base class for user-defined scalar functions.

Syntax

Visual Basic
C#

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

public abstract class SQLiteScalarFunction : SQLiteFunction, System.IDisposable

Remarks

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

The scalar function is a simple function, that returns a scalar value and is executed once when called.

To register the user-defined scalar funtion, create the class, derived from SQLiteScalarFunction and pass its name and number of arguments to the base class constructor.

You should also override the Invoke method, which should implement the function actions.

Example

Here is an example of creating and using of the function, that calculates the square root.

csharp

public class MyFunction : SQLiteScalarFunction {

        public MyFunction()
        : base("Sqrt", 1) {
        }

        protected override object Execute(object[] args, SQLiteConnection connection) {

                return Math.Sqrt(Convert.ToDouble(args[0]));
        }
}

...

SQLiteConnection sqLiteConnection = new SQLiteConnection(@"Data Source=D:\SQLite\test.db");
      sqLiteConnection.Open();
MyFunction function = new MyFunction();
      sqLiteConnection.RegisterFunction(function);
SQLiteCommand command = new SQLiteCommand("select sqrt(9.0)", sqLiteConnection);
double result = (double)command.ExecuteScalar();
      sqLiteConnection.UnRegisterFunction(function);
      sqLiteConnection.Close();

Inheritance Hierarchy

Reference

SQLiteScalarFunction Members
Devart.Data.SQLite Namespace

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