WorkbookFunctions.OverrideFunction(String, ICustomFunction) Method

Replaces the built-in function specified by its name with a custom function.

Namespace: DevExpress.Spreadsheet.Functions

Assembly: DevExpress.Spreadsheet.v19.1.Core.dll

Declaration

C#

void OverrideFunction(
    string name,
    ICustomFunction function
)

VB.NET

Sub OverrideFunction(
    name As String,
    function As ICustomFunction
)

Parameters

Name	Type	Description
name	String	A name of the function to replace.
function	ICustomFunction	An ICustomFunction descendant that is the custom function.

Remarks

Implement a custom function by creating a descendant of the FunctionWrapper class:

This example creates a function that calculates the sine of an angle measured in degrees and uses that function to replace the built-in SIN worksheet function.

The collection of worksheet functions is available by using the IWorkbook.Functions property. The WorkbookFunctions.OverrideFunction method is used to override a worksheet built-in function. The method requires the function to replace and a custom function with which the built-in function will be replaced.

To create a custom function, implement the FunctionWrapper descendant and override the FunctionWrapper.Evaluate method.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/udf-custom-function-how-to-replace-the-built-in-worksheet-function-t124453

Form1.cs

using DevExpress.Spreadsheet.Functions;
using System;
using System.Collections.Generic;
using System.Windows.Forms;
        private void ReplaceSinFunction()
        {
            WorkbookFunctions functions = spreadsheetControl1.Document.Functions;
            // Obtain the built-in function to override.
            IFunction sinFunction = functions.Math.Sin;
            // Create a new function descending from the FunctionWrapper
            // to replace the built-in function.
            OverridenFunction function = new OverridenFunction(sinFunction);
            // Substitute the built-in function with the custom function.
            functions.OverrideFunction(function.Name, function);
        }

        // A custom function that calculates the sine function for the angle measured in degerees.
        public class OverridenFunction : FunctionWrapper
        {

            public OverridenFunction(IFunction function)
                : base(function)
            {
            }

            public override ParameterValue Evaluate(IList<ParameterValue> parameters, EvaluationContext context)
            {
                ParameterValue value = parameters[0];
                if (value.IsError)
                    return value;

                double angle = parameters[0].NumericValue * Math.PI / 180;
                double sin = Math.Sin(angle);
                return Math.Round(sin, 5);
            }
        }
    }

Form1.vb

Imports DevExpress.Spreadsheet.Functions
Imports System
Imports System.Collections.Generic
Imports System.Windows.Forms
        Private Sub ReplaceSinFunction()
            Dim functions As WorkbookFunctions = spreadsheetControl1.Document.Functions
            ' Obtain the built-in function to override.
            Dim sinFunction As IFunction = functions.Math.Sin
            ' Create a new function descending from the FunctionWrapper
            ' to replace the built-in function.
            Dim [function] As New OverridenFunction(sinFunction)
            ' Substitute the built-in function with the custom function.
            functions.OverrideFunction([function].Name, [function])
        End Sub

        ' A custom function that calculates the sine function for the angle measured in degerees.
        Public Class OverridenFunction
            Inherits FunctionWrapper

            Public Sub New(ByVal [function] As IFunction)
                MyBase.New([function])
            End Sub

            Public Overrides Function Evaluate(ByVal parameters As IList(Of ParameterValue), ByVal context As EvaluationContext) As ParameterValue
                Dim value As ParameterValue = parameters(0)
                If value.IsError Then
                    Return value
                End If

                Dim angle As Double = parameters(0).NumericValue * Math.PI / 180
                Dim sin As Double = Math.Sin(angle)
                Return Math.Round(sin, 5)
            End Function
        End Class

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the OverrideFunction(String, ICustomFunction) method.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

udf-custom-function-how-to-replace-the-built-in-worksheet-function-t124453/CS/FunctionWrapperSample/Form1.cs#L36

    // Substitute the built-in function with the custom function.
    functions.OverrideFunction(function.Name, function);
}

VB.NET

udf-custom-function-how-to-replace-the-built-in-worksheet-function-t124453/VB/FunctionWrapperSample/Form1.vb#L33

    ' Substitute the built-in function with the custom function.
    functions.OverrideFunction([function].Name, [function])
End Sub