Winforms Data Grid - Calculate a summary against detail rows and display it in a master row cell

C#
using System;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using DevExpress.XtraGrid.Views.Grid;
using DevExpress.XtraGrid.Columns;

namespace WindowsApplication59
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            InitData();

            gridControl1.UseEmbeddedNavigator = true;
            gridControl1.ForceInitialize();
            GridColumn col = gridView1.Columns.AddField("Tasks");
            col.UnboundType = DevExpress.Data.UnboundColumnType.Integer;
            col.Visible = true;
            gridView1.CustomUnboundColumnData+=new DevExpress.XtraGrid.Views.Base.CustomColumnDataEventHandler(gridView1_CustomUnboundColumnData);
        }

        private void gridView1_CustomUnboundColumnData(object sender, DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs e)
        {
            GridView view = sender as GridView;
            if (e.Column.FieldName != "Tasks") return;
            if (!e.IsGetData) return;
            DataRow row = ((view.DataSource as IList)[e.ListSourceRowIndex] as DataRowView).Row;
            e.Value = row.GetChildRows("Project_Tasks").Length;
        }

        void InitData()
        {
            dataTable1.Rows.Add(new object[] { 0, "Software", 4000 });
            dataTable1.Rows.Add(new object[] { 1, "Hardware", 1500 });
            dataTable1.Rows.Add(new object[] { 2, "Project X", 100000 });
            dataTable2.Rows.Add(new object[] { null, 0, "Drivers" });
            dataTable2.Rows.Add(new object[] { null, 0, "Application" });
            dataTable2.Rows.Add(new object[] { null, 1, "All the stuff" });
            dataTable2.Rows.Add(new object[] { null, 2, "Part X" });
            dataTable2.Rows.Add(new object[] { null, 2, "Part Y" });
            dataTable2.Rows.Add(new object[] { null, 2, "Part Z" });
        }
    }
}

Visual Basic
Imports System.Collections
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Windows.Forms
Imports DevExpress.XtraGrid.Views.Grid
Imports DevExpress.XtraGrid.Columns

Namespace WindowsApplication59

    Public Partial Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
            InitData()
            gridControl1.UseEmbeddedNavigator = True
            gridControl1.ForceInitialize()
            Dim col As GridColumn = gridView1.Columns.AddField("Tasks")
            col.UnboundType = DevExpress.Data.UnboundColumnType.Integer
            col.Visible = True
            AddHandler gridView1.CustomUnboundColumnData, New DevExpress.XtraGrid.Views.Base.CustomColumnDataEventHandler(AddressOf gridView1_CustomUnboundColumnData)
        End Sub

        Private Sub gridView1_CustomUnboundColumnData(ByVal sender As Object, ByVal e As DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs)
            Dim view As GridView = TryCast(sender, GridView)
            If Not Equals(e.Column.FieldName, "Tasks") Then Return
            If Not e.IsGetData Then Return
            Dim row As DataRow = TryCast(TryCast(view.DataSource, IList)(e.ListSourceRowIndex), DataRowView).Row
            e.Value = row.GetChildRows("Project_Tasks").Length
        End Sub

        Private Sub InitData()
            dataTable1.Rows.Add(New Object() {0, "Software", 4000})
            dataTable1.Rows.Add(New Object() {1, "Hardware", 1500})
            dataTable1.Rows.Add(New Object() {2, "Project X", 100000})
            dataTable2.Rows.Add(New Object() {Nothing, 0, "Drivers"})
            dataTable2.Rows.Add(New Object() {Nothing, 0, "Application"})
            dataTable2.Rows.Add(New Object() {Nothing, 1, "All the stuff"})
            dataTable2.Rows.Add(New Object() {Nothing, 2, "Part X"})
            dataTable2.Rows.Add(New Object() {Nothing, 2, "Part Y"})
            dataTable2.Rows.Add(New Object() {Nothing, 2, "Part Z"})
        End Sub
    End Class
End Namespace