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ICustomCalculationService.OnBeginCellCalculation(CellCalculationArgs) Method

Called when the calculation is started for a particular cell.

Namespace: DevExpress.XtraSpreadsheet.Services

Assembly: DevExpress.Spreadsheet.v24.2.Core.dll

NuGet Package: DevExpress.Spreadsheet.Core

#Declaration

void OnBeginCellCalculation(
    CellCalculationArgs args
)

#Parameters

Name Type Description
args CellCalculationArgs

A instance which allows you to identify a cell and obtain its value before calculation.

#Remarks

If circular references are found, the OnBeginCellCalculation method for the cell with circular reference is called two times. Subsequently, the ICustomCalculationService.OnBeginCircularReferencesCalculation method is called, and the ICustomCalculationService.OnEndCircularReferencesCalculation is called if the ICustomCalculationService.OnBeginCircularReferencesCalculation method did not return false. In this situation, the ICustomCalculationService.OnEndCellCalculation method is not called at all.

#Example

This example illustrates the use of the service which implements the ICustomCalculationService interface and allows to manage the process of worksheet calculations.

The application creates log entries when worksheet calculation starts and finishes, when cell calculation begins and ends, when a cell with the circular reference starts and finishes its calculation.

using DevExpress.Spreadsheet;
using DevExpress.Spreadsheet.Formulas;
using DevExpress.XtraTreeList.Nodes;
using System;
using System.Collections.Generic;
    public class TestCustomCalculationService : DevExpress.XtraSpreadsheet.Services.ICustomCalculationService {
        private DevExpress.XtraTreeList.TreeList loggingControl;
        private TreeListNode rootListNode = null;
        public HashSet<CellKey> CircularReferencedCells = new HashSet<CellKey>();

        public TestCustomCalculationService(object controlForLogging)
        {
            loggingControl = controlForLogging as DevExpress.XtraTreeList.TreeList;
        }

        public bool OnBeginCalculation() {
            // Set the root node for displaying info on the current calculation.
            rootListNode = loggingControl.AppendNode(new object[] {String.Format("Calculation starts at {0}", DateTime.Now)}, null);
            // To highlight cells with circular references, this example uses a hash set of such cells. 
            // Clear it when a new calculation starts.
            CircularReferencedCells.Clear();
            // True to perform a calculation. Return False to cancel it.
            return true;
        }
        public void OnBeginCellCalculation(CellCalculationArgs args) {
            // Add a record about the cell being calculated.
            CreateLogEntry("Cell calculation begins", new string[] {String.Format("CellKey: ({0})", args.CellKey)} );
        }
        public bool OnBeginCircularReferencesCalculation() {
            // Indicate that a circular reference calculation starts. 
            // If the SpreadsheetControl.Document.DocumentSettings.Calculation.Iterative property is false (default),
            // this method is not called.
            // If a circular reference calculation starts, the OnBeginCellCalculation method is called again.
            CreateLogEntry("Circular Reference calculation begins", new string[] {});
            // True to perform a calculation. Return False to cancel it.
            return true;
        }
        public void OnEndCalculation() {
            // Add a record that the calculation has finished.
            CreateLogEntry(String.Format("Calculation finishes at {0}", DateTime.Now), new string[] {});
            rootListNode = null;
        }
        public void OnEndCellCalculation(CellKey cellKey, CellValue startValue, CellValue endValue) {
            // Display cell information, a cell value before calculation and the calculated cell value.
            string info = String.Format("CellKey: ({0}) Before: {1}, After: {2}", cellKey, startValue, endValue);
            CreateLogEntry("Cell calculation ends", new string[] {info} );
        }
        public void OnEndCircularReferencesCalculation(IList<CellKey> cellKeys) {
            // Store cell keys of cells with circular references for further use.
            CircularReferencedCells = new HashSet<DevExpress.Spreadsheet.CellKey>(cellKeys); 
            string[] sKeys = new string[cellKeys.Count];
            int i = 0;
            foreach (CellKey key in cellKeys) {
                sKeys[i] = key.ToString();
                i++;
            } 
            // Display the information on cells with circular references.
            CreateLogEntry("Circular Reference calculation ends", sKeys);
        }
        public bool ShouldMarkupCalculateAlwaysCells() {
            // Mark as needing calculation the "calculate always" cells, 
            // such as cells containing volatile function or referencing another "calculate always" cell.
            return true;
        }

        private void CreateLogEntry(string actionName, string[] info)
        {
            TreeListNode firstLevelNode = loggingControl.AppendNode(new object[] { actionName }, rootListNode);
            if (info.Length != 0)
            {
                for (int i = 0; i < info.Length; i++)
                {
                    TreeListNode secondLevelNode = loggingControl.AppendNode(new object[] { info[i] }, firstLevelNode);
                }
            }
            firstLevelNode.ExpandAll();
            loggingControl.MakeNodeVisible(firstLevelNode);
        }
    }
See Also