WinForms Data Grid - Asynchronously load data into an unbound column

C#
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using DevExpress.XtraEditors;
using System.Data.OleDb;
using System.Threading;
using System.Runtime.Remoting.Messaging;


namespace DXSample {
    public partial class Main: XtraForm {
        string connectionSting = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\nwind.mdb";
        Dictionary<int, object> unboundValues = new Dictionary<int, object>();
        private delegate KeyValuePair<int, object> GetDataDelegate(int index);

        public Main() {
            InitializeComponent();
        }

        private void OnFormLoad(object sender, EventArgs e) {
            this.ordersTableAdapter.Fill(this.nwindDataSet.Orders);
        }

        private void OnCustomUnboundColumnData(object sender, DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs e)
        {
            if (e.Column.FieldName == "Quantity")
                if (e.IsGetData)
                {
                    object val = GetSummaryValue(e);
                    e.Value = val;
                }
        }

        private object GetSummaryValue(DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs e)
        {
            if (unboundValues.ContainsKey(e.ListSourceRowIndex)) return unboundValues[e.ListSourceRowIndex];
            unboundValues.Add(e.ListSourceRowIndex, "Not Loaded");
            GetDataAsync(e.ListSourceRowIndex);
            return unboundValues[e.ListSourceRowIndex];
        }

        private void GetDataAsync(int index)
        {
            GetDataDelegate d = new GetDataDelegate(GetData);
            d.BeginInvoke(index, new AsyncCallback(DataLoaded), null);
        }

        KeyValuePair<int, object> GetData(int index) {
            int id = Convert.ToInt32(nwindDataSet.Orders[index]["OrderID"]);
            OleDbConnection connection = new OleDbConnection(connectionSting);
            connection.Open();
            string cmdText = string.Format("SELECT SUM({0}) FROM {1} WHERE {2} = {3}", "Quantity", "OrderDetails", "OrderID", id);
            OleDbCommand command = new OleDbCommand(cmdText, connection);
            object val = command.ExecuteScalar();
            Thread.Sleep(500);
            connection.Close();
            return new KeyValuePair<int, object>(index, val);
        }

         void DataLoaded(IAsyncResult r) {
            GetDataDelegate d = (r as AsyncResult).AsyncDelegate as GetDataDelegate;
            KeyValuePair<int, object> pair = (KeyValuePair<int, object>)d.EndInvoke(r);
            unboundValues[pair.Key] = pair.Value;
            UpdateGrid();
        }

        private void UpdateGrid()
        {
            if (gridControl1.InvokeRequired)
                gridControl1.Invoke(new MethodInvoker(delegate{
                    gridView1.LayoutChanged();
                }));
            else
                gridView1.LayoutChanged();
        }
    }
}

Visual Basic
Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Imports DevExpress.XtraEditors
Imports System.Data.OleDb
Imports System.Threading
Imports System.Runtime.Remoting.Messaging


Namespace DXSample
    Partial Public Class Main
        Inherits XtraForm
        Private connectionSting As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\nwind.mdb"
        Private unboundValues As New Dictionary(Of Integer, Object)()
        Private Delegate Function GetDataDelegate(ByVal index As Integer) As KeyValuePair(Of Integer, Object)

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub OnFormLoad(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
            Me.ordersTableAdapter.Fill(Me.nwindDataSet.Orders)
        End Sub

        Private Sub OnCustomUnboundColumnData(ByVal sender As Object, ByVal e As DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs) Handles gridView1.CustomUnboundColumnData
            If e.Column.FieldName = "Quantity" Then
                If e.IsGetData Then
                    Dim val As Object = GetSummaryValue(e)
                    e.Value = val
                End If
            End If
        End Sub

        Private Function GetSummaryValue(ByVal e As DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs) As Object
            If unboundValues.ContainsKey(e.ListSourceRowIndex) Then
                Return unboundValues(e.ListSourceRowIndex)
            End If
            unboundValues.Add(e.ListSourceRowIndex, "Not Loaded")
            GetDataAsync(e.ListSourceRowIndex)
            Return unboundValues(e.ListSourceRowIndex)
        End Function

        Private Sub GetDataAsync(ByVal index As Integer)
            Dim d As New GetDataDelegate(AddressOf GetData)
            d.BeginInvoke(index, New AsyncCallback(AddressOf DataLoaded), Nothing)
        End Sub

        Private Function GetData(ByVal index As Integer) As KeyValuePair(Of Integer, Object)
            Dim id As Integer = Convert.ToInt32(nwindDataSet.Orders(index)("OrderID"))
            Dim connection As New OleDbConnection(connectionSting)
            connection.Open()
            Dim cmdText As String = String.Format("SELECT SUM({0}) FROM {1} WHERE {2} = {3}", "Quantity", "OrderDetails", "OrderID", id)
            Dim command As New OleDbCommand(cmdText, connection)
            Dim val As Object = command.ExecuteScalar()
            Thread.Sleep(500)
            connection.Close()
            Return New KeyValuePair(Of Integer, Object)(index, val)
        End Function

         Private Sub DataLoaded(ByVal r As IAsyncResult)
            Dim d As GetDataDelegate = TryCast((TryCast(r, AsyncResult)).AsyncDelegate, GetDataDelegate)
            Dim pair As KeyValuePair(Of Integer, Object) = CType(d.EndInvoke(r), KeyValuePair(Of Integer, Object))
            unboundValues(pair.Key) = pair.Value
            UpdateGrid()
         End Sub

        Private Sub UpdateGrid()
            If gridControl1.InvokeRequired Then
                gridControl1.Invoke(New MethodInvoker(AddressOf gridView1.LayoutChanged))
            Else
                gridView1.LayoutChanged()
            End If
        End Sub
      
    End Class
End Namespace