Hi - 

 I am having a problem exporting hierarchical data from an UltraWebGrid to Excel in one scenario:  When the first parent row has no children.  It took me a while to figure out what the problem was.  Basically I have one on-screen grid with paging that shows the records fine in all scenarios.  Since it has paging, when the user clicks an Export button I create a second, non-paged grid in code and pass that to the Excel exporter control.  However, when I bind the hierarchical DataSet to the programmatically created grid, I get an "Object reference not set to an instance of an object" error *only* if the first row has no children.  

 To illustrate the problem I created a simple console app that uses a manually created DataSet that I borrowed from an Infragistics How To article.  This is the whole thing:

using System;
using System.Data;
using System.Diagnostics;

//the project also needs references to System.Xml and Infragistics.WebUI.Shared

using Infragistics.WebUI.UltraWebGrid;

namespace GridExportProblem
{
    class Program
    {
        private enum ChildRowMode
        {
            AllHaveChildren,
            FirstHaveChildren,
            LastHaveChildren
        }

        static void Main(string[] args)
        {
            CreateGrid(ChildRowMode.AllHaveChildren);
            CreateGrid(ChildRowMode.FirstHaveChildren);

            //this blows up

            CreateGrid(ChildRowMode.LastHaveChildren);
        }

        private static void CreateGrid(ChildRowMode childRowMode)
        {
            DataSet ds = GetDataset(childRowMode);

            UltraWebGrid uwg = new UltraWebGrid("myGrid");
            // Set the WebGrid's view type to Hierarchical
            uwg.DisplayLayout.ViewType =
              Infragistics.WebUI.UltraWebGrid.ViewType.Hierarchical;

            uwg.DataSource = ds.Tables["Customer"];

            Debug.WriteLine("Binding grid with ChildRowMode " + childRowMode.ToString());

            try
            {
                uwg.DataBind();
                Debug.WriteLine("Success!");
            }
            catch (Exception ex)
            {
                Debug.WriteLine("Failure.  Error: " + ex.Message);
                Debug.WriteLine(ex.StackTrace);
            }
        }


        private static DataSet GetDataset(ChildRowMode childRowMode)
        {
            DataSet ds = new DataSet();

            // Customer DataTable
            DataTable dt = new DataTable("Customer");
            dt.Columns.Add("CustomerID", typeof(int));
            dt.Columns.Add("CustomerName", typeof(string));
            dt.Columns.Add("Date", typeof(DateTime));
            dt.Rows.Add(new object[] { 1, "John Lever", DateTime.Now });
            dt.Rows.Add(new object[] { 2, "Walter Smith", DateTime.Now.AddDays(1) });
            dt.Rows.Add(new object[] { 3, "Kathy Lever", DateTime.Now.AddDays(2) });
            dt.Rows.Add(new object[] { 4, "George Wills", DateTime.Now.AddDays(3) });
            ds.Tables.Add(dt);

            // Orders DataTable
            dt = new DataTable("Orders");
            dt.Columns.Add("OrderID", typeof(int));
            dt.Columns.Add("ProductName", typeof(string));
            dt.Columns.Add("Price", typeof(double));
            dt.Columns.Add("Quantity", typeof(int));

            if ((childRowMode == ChildRowMode.FirstHaveChildren) || (childRowMode == ChildRowMode.AllHaveChildren))
            {
                dt.Rows.Add(new object[] { 1, "Bolts", 2.30, 15 });
                dt.Rows.Add(new object[] { 1, "Screws", 2.03, 55 });
                dt.Rows.Add(new object[] { 1, "Nails", 1.01, 25 });
                dt.Rows.Add(new object[] { 2, "Bolts", 2.30, 65 });
                dt.Rows.Add(new object[] { 2, "Screws", 2.03, 75 });
                dt.Rows.Add(new object[] { 2, "Nails", 1.01, 95 });
            }

            if ((childRowMode == ChildRowMode.LastHaveChildren) || (childRowMode == ChildRowMode.AllHaveChildren))
            {
                dt.Rows.Add(new object[] { 3, "Bolts", 2.30, 65 });
                dt.Rows.Add(new object[] { 3, "Screws", 2.03, 205 });
                dt.Rows.Add(new object[] { 3, "Nails", 1.01, 265 });
                dt.Rows.Add(new object[] { 4, "Bolts", 2.30, 695 });
            }

            ds.Tables.Add(dt);

            // Create customers/orders relationship and add to DataSet
            ds.Relations.Add("Customer_Order", ds.Tables["Customer"].Columns["CustomerID"],
                ds.Tables["Orders"].Columns["OrderID"]);

            return ds;


        }
    }
}