How to: Use Asynchronous Operations That Return the Result

• Nov 13, 2018
• 3 minutes to read

This example shows how to use asynchronous operations that return the result.

In this example, the PivotGridControl.CellClick event is handled to generate a drill-down data source for a specific cell using the PivotGridControl.CreateDrillDownDataSourceAsync method. The AsyncCompletedHandler delegate is passed as a method parameter. The referenced method is executed after the operation is completed, allowing to obtain the result via the result parameter of the delegate. This parameter returns an AsyncOperationResult instance.

The AsyncOperationResult.Value property is used to obtain a record set associated with the clicked cell. Then, the PivotDrillDownDataSource.RowCount property is used to determine the number of records in the data source for this cell.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-use-asynchronous-operations-that-return-the-result-e4567

Form1.cs

using System;
using System.Windows.Forms;
using DevExpress.XtraPivotGrid;

namespace XtraPivotGrid_CreateDrillDownDataSourceAsync {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {

            // Binds the pivot grid to data.
            this.salesPersonTableAdapter.Fill(this.nwindDataSet.SalesPerson);
        }

        private void pivotGridControl1_CellClick(object sender, 
            DevExpress.XtraPivotGrid.PivotCellEventArgs e) {
            PivotGridControl pivot = sender as PivotGridControl;

            //Checks whether an asynchronous operation is in progress.
            if (!pivot.IsAsyncInProgress)

                // Gets the record set associated with the clicked cell.
                // The delegate is passed to obtain this record set.
                pivot.CreateDrillDownDataSourceAsync(e.ColumnIndex, e.RowIndex, result => {

                    // The 'result' parameter of the delegate returns an AsyncOperationResult instance.
                    // The AsyncOperationResult.Value property is used to obtain the record set, 
                    // the PivotDrillDownDataSource.RowCount property is used to obtain the number 
                    // of records in the data source.
                    label1.Text = "RowCount = " + ((PivotDrillDownDataSource)result.Value).RowCount;
                });
        }
    }
}

Form1.vb

Imports System
Imports System.Windows.Forms
Imports DevExpress.XtraPivotGrid

Namespace XtraPivotGrid_CreateDrillDownDataSourceAsync
    Partial Public Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load

            ' Binds the pivot grid to data.
            Me.salesPersonTableAdapter.Fill(Me.nwindDataSet.SalesPerson)
        End Sub

        Private Sub pivotGridControl1_CellClick(ByVal sender As Object, ByVal e As DevExpress.XtraPivotGrid.PivotCellEventArgs) Handles pivotGridControl1.CellClick
            Dim pivot As PivotGridControl = TryCast(sender, PivotGridControl)

            'Checks whether an asynchronous operation is in progress.
            If Not pivot.IsAsyncInProgress Then

                ' Gets the record set associated with the clicked cell.
                ' The delegate is passed to obtain this record set.
                pivot.CreateDrillDownDataSourceAsync(e.ColumnIndex, e.RowIndex, Sub(result) label1.Text = "RowCount = " & CType(result.Value, PivotDrillDownDataSource).RowCount)
            End If
                    ' The 'result' parameter of the delegate returns an AsyncOperationResult instance.
                    ' The AsyncOperationResult.Value property is used to obtain the record set, 
                    ' the PivotDrillDownDataSource.RowCount property is used to obtain the number 
                    ' of records in the data source.
        End Sub
    End Class
End Namespace