Tahnk you Maya, it work correctly.

So, i have two others question please.

1/ for the last example how can do this with C#

I tried with this Code

            BoundDataField boundField = new BoundDataField(true);

            boundField.Key = "CategoryID";

            boundField.Header.Text = "Category ID";

            boundField.DataFieldName = "CategoryID";

            this.WebHierarchicalDataGrid1.Columns.Add(boundField);

            Band childBand = new Band();

            childBand.DataKeyFields = "ProductID";

            childBand.DataMember = "Product";

            this.WebHierarchicalDataGrid1.Bands.Add(childBand);

            // Define column for the child band

            boundField = new BoundDataField(true);

            boundField.Key = "ProductID";

            boundField.Header.Text = "Product ID";

            boundField.DataFieldName = "ProductID";

            this.WebHierarchicalDataGrid1.Bands["Product"].Columns.Add(boundField);

but i have this error:

Object reference not set to an instance of an object.

Line 53:             boundField.DataFieldName = "ProductID";
Line 54: 
Line 55:             this.WebHierarchicalDataGrid1.Bands["Product"].Columns.Add(boundField);

2/ How can i do it with an XML File like this?

<Item><Category>2- category 2</Category><Title>title 21</Title><Key>A5</Key></Item>

I tried it with this code but it doesn't work:

<asp:XmlDataSource ID="XmlDataSource1" runat="server" DataFile="~/Model.xml" XPath="/ItemList/Item"></asp:XmlDataSource>

<ig:WebHierarchicalDataGrid ID="WebHierarchicalDataGrid1" runat="server" 

   AutoGenerateBands="False" AutoGenerateColumns="False" 

   DataSourceID="XmlDataSource1" Key="Category">

   <Columns>

            <ig:BoundDataField  DataFormatString="Category" Key="Category" Header-Text="Category" />

    </Columns>

    <Bands>

         <ig:Band AutoGenerateColumns="False" DataMember="Title" DataKeyFields="Title">

              <Columns>

                     <ig:BoundDataField DataFieldName="Title" Key="Title" Header-Text="Title" />

                     <ig:BoundDataField DataFieldName="Key" Key="Key" Header-Text="Key" />

                </Columns>

         </ig:Band>

    </Bands>

</ig:WebHierarchicalDataGrid>