C# create hierarchical GridView with Telerik UI for WinForms with SQL Query

Question

I tried to create a hierarchical GridView with Telerik UI for WinForms with two SQL queries for getting data.

I found this code example: http://www.telerik.com/help/winforms/gridview-hierarchical-grid-binding-to-hierarchical-data-programmatically.html

But they use a Northwind DataSet. (I will not connect to my SQL database via VS2008 SQL Connection Wizard.)

private void LoadUnboundData()
{
    using (radGridView1.DeferRefresh())
    {
        for (int i = 0; i < nwindDataSet.Employees.Count; i++)
        ...

How can I use my own dataselection via SQLDataReader?

I am working with Visual Studio 2008 using C# and a SQL Express 2012 Server with AdventureWorks database examples.

Suggestions are welcome Best Regards

Answer 1

I am not positive if you'd like to do this "OnDemand" or preload everything at once. You can begin by referring to an answer I provided on the Telerik forum for an OnDemand load and alter it to fit your needs. The logic will use a datatable that you can load from any source like ODBC.

Link: https://www.telerik.com/forums/ondemand-hierarchical-datagrid#Cy41z5kzRUG-44fhLidpeQ

Code Example:

using System;
using System.Data;
using Telerik.WinControls.UI;

namespace example
{
    public partial class frmtest : Telerik.WinControls.UI.RadForm
    {
        private DataTable _parentData = new DataTable();

        public frmtest()
        {
            InitializeComponent();
        }

        private void frmtest_Load(object sender, EventArgs e)
        {
            _parentData = exampleParentDataTableLoad(); // Replace with call to populate a datatable from a query
            loadGridAndParentRecords();
        }

        private void loadGridAndParentRecords()
        {
            exampleRadGridView.DataSource = _parentData;
            var _childTemplate = CreateChildTemplate();
            exampleRadGridView.Templates.Add(_childTemplate);
            _childTemplate.HierarchyDataProvider = new GridViewEventDataProvider(_childTemplate);
            exampleRadGridView.RowSourceNeeded += ExampleRadGridView_RowSourceNeeded;
        }

        private GridViewTemplate CreateChildTemplate()
        {
            GridViewTemplate template = new GridViewTemplate();
            template.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
            template.Columns.Add(new GridViewTextBoxColumn
            {
                Name = "Id",
                HeaderText = "ID"
            });
            template.Columns.Add(new GridViewTextBoxColumn
            {
                Name = "SampleNumber",
                HeaderText = "Sample Number"
            });
            template.Columns.Add(new GridViewTextBoxColumn
            {
                Name = "ParentId",
                HeaderText = "Parent Id"
            });

            return template;
        }

        private void ExampleRadGridView_RowSourceNeeded(object sender, Telerik.WinControls.UI.GridViewRowSourceNeededEventArgs e)
        {
            if (e.ParentRow != null)
            {
                if (e.ParentRow.DataBoundItem is DataRowView rowViewData)
                {
                    var _childDataTable = exampleChildTableLoad(); // Replace with call to populate a datatable from a query

                    var _dataRows = _childDataTable.Select($"ParentId = {rowViewData["Id"]}");

                    foreach (DataRow row in _dataRows)
                    {
                        GridViewRowInfo _newRowObj = e.Template.Rows.NewRow();
                        _newRowObj.Cells["Id"].Value = row["Id"];
                        _newRowObj.Cells["SampleNumber"].Value = row["SampleNumber"];
                        _newRowObj.Cells["ParentId"].Value = row["ParentId"];
                        e.SourceCollection.Add(_newRowObj);
                    }
                }
            }
        }

        private DataTable exampleParentDataTableLoad()
        {
            DataTable _return = new DataTable();
            _return.Columns.Add("Id", typeof(int));
            _return.Columns.Add("DisplayName", typeof(string));

            _return.Rows.Add(1, "Test1");
            _return.Rows.Add(2, "Test2");

            return _return;
        }

        private DataTable exampleChildTableLoad()
        {
            DataTable _return = new DataTable();
            _return.Columns.Add("Id", typeof(int));
            _return.Columns.Add("SampleNumber", typeof(string));
            _return.Columns.Add("ParentId", typeof(int));

            _return.Rows.Add(9999, "Test1", 2);
            _return.Rows.Add(9998, "Test2", 2);
            _return.Rows.Add(9997, "Test3", 2);
            _return.Rows.Add(9996, "Test4", 1);
            _return.Rows.Add(9995, "Test5", 1);
            _return.Rows.Add(9994, "Test6", 1);

            return _return;
        }
    }
}