The following example shows a load-on-demand scenario using a typed DataSet. Let have the following Products data from the AdventureWorks database:

Steps to create a Load-On-Demand hierarchy mode:

1. First, create a columns schema for the first (parent) level of the hierarchy. If RadGridView is in a data-bound mode and we do not need to set a custom schema, we can just set the DataSource property of RadGridView which will set the schema and will populate the parent level with data. You can also set the AutoSizeColumnsMode to Fill to get a better view of the data:
2. Then, create a Child template and a columns schema for the ‘Product’ data:
   Copy[C#] Defining the child template

   private GridViewTemplate CreateChildTemplate()
   {
       GridViewTemplate template = new GridViewTemplate();
       template.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
   
       GridViewTextBoxColumn namecolumn = new GridViewTextBoxColumn("Name");
       GridViewTextBoxColumn productNumberColumn = new GridViewTextBoxColumn("ProductNumber");
       GridViewTextBoxColumn colorColumn = new GridViewTextBoxColumn("Color");
       GridViewDecimalColumn listPriceColumn = new GridViewDecimalColumn("ListPrice");
       GridViewTextBoxColumn sizeColumn = new GridViewTextBoxColumn("Size");
       GridViewDecimalColumn weightColumn = new GridViewDecimalColumn("Weight");
       GridViewDateTimeColumn discontinuedColumn = new GridViewDateTimeColumn("DiscontinuedDate");
       template.Columns.AddRange(namecolumn,
           productNumberColumn,
           colorColumn,
           listPriceColumn,
           sizeColumn,
           weightColumn,
           discontinuedColumn);
   
       return template;
   }

   Copy[VB.NET] Defining the child template

   Private Function CreateChildTemplate() As GridViewTemplate
       Dim template As New GridViewTemplate()
       template.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill
   
       Dim namecolumn As New GridViewTextBoxColumn("Name")
       Dim productNumberColumn As New GridViewTextBoxColumn("ProductNumber")
       Dim colorColumn As New GridViewTextBoxColumn("Color")
       Dim listPriceColumn As New GridViewDecimalColumn("ListPrice")
       Dim sizeColumn As New GridViewTextBoxColumn("Size")
       Dim weightColumn As New GridViewDecimalColumn("Weight")
       Dim discontinuedColumn As New GridViewDateTimeColumn("DiscontinuedDate")
       template.Columns.AddRange(namecolumn, productNumberColumn, colorColumn, listPriceColumn, sizeColumn, weightColumn, discontinuedColumn)
   
       Return template
   End Function

3. Setup the load-on-demand mode by using GridViewEventDataProvider and RowSourceNeeded event:
   Copy[C#] Setting up the load-on-demand mode

   void Form1_Load(object sender, EventArgs e)
   {
       this.productModelTableAdapter.Fill(this.adventureLT2008DataSet.ProductModel);
       this.productTableAdapter.Fill(this.adventureLT2008DataSet.Product);
   
       GridViewTemplate childTemplate = CreateChildTemplate();
       this.radGridView1.Templates.Add(childTemplate);
   
       childTemplate.HierarchyDataProvider = new GridViewEventDataProvider(childTemplate);
       this.radGridView1.RowSourceNeeded += new GridViewRowSourceNeededEventHandler(radGridView1_RowSourceNeeded);
   }

   Copy[VB.NET] Setting up the load-on-demand mode

   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Me.ProductModelTableAdapter.Fill(Me.AdventureLT2008DataSet.ProductModel)
       Me.ProductTableAdapter.Fill(Me.AdventureLT2008DataSet.Product)
   
       Dim childTemplate As GridViewTemplate = CreateChildTemplate()
       Me.RadGridView1.Templates.Add(childTemplate)
   
       childTemplate.HierarchyDataProvider = New GridViewEventDataProvider(childTemplate)
       AddHandler RadGridView1.RowSourceNeeded, AddressOf radGridView1_RowSourceNeeded
   End Sub

4. Load the data on demand for an expanded parent row by using the RowSourceNeeded event:
   Copy[C#] Handling RowSourceNeeded event

   void radGridView1_RowSourceNeeded(object sender, GridViewRowSourceNeededEventArgs e)
   {
       DataRowView rowView = e.ParentRow.DataBoundItem as DataRowView;
       DataRow[] rows = rowView.Row.GetChildRows("ProductModel_Product");
   
       foreach (DataRow dataRow in rows)
       {
           GridViewRowInfo row = e.Template.Rows.NewRow();
           row.Cells["Name"].Value = dataRow["Name"];
           row.Cells["ProductNumber"].Value = dataRow["ProductNumber"];
           row.Cells["Color"].Value = dataRow["Color"];
           row.Cells["ListPrice"].Value = dataRow["ListPrice"];
           row.Cells["Size"].Value = dataRow["Size"];
           row.Cells["Weight"].Value = dataRow["Weight"];
           row.Cells["DiscontinuedDate"].Value = dataRow["DiscontinuedDate"];
   
           e.SourceCollection.Add(row);
       }
   }

   Copy[VB.NET] Handling RowSourceNeeded event

   Private Sub radGridView1_RowSourceNeeded(ByVal sender As Object, ByVal e As GridViewRowSourceNeededEventArgs)
       Dim rowView As DataRowView = TryCast(e.ParentRow.DataBoundItem, DataRowView)
       Dim rows() As DataRow = rowView.Row.GetChildRows("ProductModel_Product")
   
       For Each dataRow As DataRow In rows
           Dim row As GridViewRowInfo = e.Template.Rows.NewRow()
           row.Cells("Name").Value = dataRow("Name")
           row.Cells("ProductNumber").Value = dataRow("ProductNumber")
           row.Cells("Color").Value = dataRow("Color")
           row.Cells("ListPrice").Value = dataRow("ListPrice")
           row.Cells("Size").Value = dataRow("Size")
           row.Cells("Weight").Value = dataRow("Weight")
           row.Cells("DiscontinuedDate").Value = dataRow("DiscontinuedDate")
   
           e.SourceCollection.Add(row)
       Next dataRow
   End Sub