private DataSet weddingPlan;
public DataSet WeddingPlan {
    get 
    { 
        if(weddingPlan == null)
        {
            weddingPlan = new DataSet();
            using (StreamReader rdr = new StreamReader("TelerikWeddingPlanner.xml"))
            {
                weddingPlan.ReadXml(rdr);
            }
        }

        return weddingPlan;
    }
}

public Form1()
{
    InitializeComponent();

    // Events
    this.radGanttView1.GanttViewElement.EditorRequired += GanttViewElement_EditorRequired;
    this.radGanttView1.GanttViewElement.EditorInitialized += GanttViewElement_EditorInitialized;
    this.radGanttView1.GanttViewElement.ItemValidating += GanttViewElement_ItemValidating;
    this.radGanttView1.GanttViewElement.ItemValidated += GanttViewElement_ItemValidated;
    this.radGanttView1.GanttViewElement.ItemEdited += GanttViewElement_ItemEdited;
}

private void GanttViewElement_DoubleClick(object sender, EventArgs e)
{
    Debug.WriteLine("GanttViewElement_DoubleClick");
}

private void GanttViewElement_EditorRequired(object sender, GanttViewEditorRequiredEventArgs e)
{
    Debug.WriteLine("GanttViewElement_EditorRequired");
    
}

private void GanttViewElement_EditorInitialized(object sender, GanttViewItemEditorInitializedEventArgs e)
{
    Debug.WriteLine("GanttViewElement_EditorInitialized");
    
}

private void GanttViewElement_ItemValidated(object sender, GanttViewItemValidatedEventArgs e)
{
    Debug.WriteLine("GanttViewElement_ItemValidated");
    
}

private void GanttViewElement_ItemValidating(object sender, GanttViewItemValidatingEventArgs e)
{
    Debug.WriteLine("GanttViewElement_ItemValidating");
    Debug.WriteLine(e.Column.FieldName);
    e.Cancel = true;
}

private void GanttViewElement_ItemEdited(object sender, GanttViewItemEditedEventArgs e)
{
    Debug.WriteLine("GanttViewElement_ItemEdited");
    
}

private void Form1_Load(object sender, EventArgs e)
{
    this.radGanttView1.DataSource = WeddingPlan;


    this.radGanttView1.GanttViewElement.TaskDataMember = "Tasks";
    this.radGanttView1.GanttViewElement.ChildMember = "Id";
    this.radGanttView1.GanttViewElement.ParentMember = "ParentId";
    this.radGanttView1.GanttViewElement.TitleMember = "Title";
    this.radGanttView1.GanttViewElement.StartMember = "Start";
    this.radGanttView1.GanttViewElement.EndMember = "Finish";
    this.radGanttView1.GanttViewElement.ProgressMember = "Progress";
    this.radGanttView1.GanttViewElement.LinkDataMember = "Links";
    this.radGanttView1.GanttViewElement.LinkStartMember = "StartId";
    this.radGanttView1.GanttViewElement.LinkEndMember = "EndId";
    this.radGanttView1.GanttViewElement.LinkTypeMember = "LinkType";

    this.radGanttView1.GanttViewElement.Columns.Add(new GanttViewTextViewColumn("Id"));
    this.radGanttView1.GanttViewElement.Columns.Add(new GanttViewTextViewColumn("ParentId"));
    this.radGanttView1.GanttViewElement.Columns.Add(new GanttViewTextViewColumn("Title"));
    this.radGanttView1.GanttViewElement.Columns.Add(new GanttViewTextViewColumn("Start"));
    this.radGanttView1.GanttViewElement.Columns.Add(new GanttViewTextViewColumn("Finish"));

    this.radGanttView1.GanttViewElement.Columns[0].Visible = false;
    this.radGanttView1.GanttViewElement.Columns[1].Visible = false;
    this.radGanttView1.GanttViewElement.Columns[2].Width = 350;
    this.radGanttView1.GanttViewElement.Columns[3].Width = 120;
    this.radGanttView1.GanttViewElement.Columns[4].Width = 120;

    this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineRange = TimeRange.Month;
    this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineStart = new DateTime(2006, 8, 21);
    this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineEnd = new DateTime(2007, 4, 3);

}

private void radGanttView1_ItemChildIdNeeded(object sender, GanttViewItemChildIdNeededEventArgs e)
{
    int max = int.MinValue;
    foreach (DataRow row in (this.radGanttView1.DataSource as DataSet).Tables[0].Rows)
    {
        if (int.Parse(row[0].ToString()) > max)
        {
            max = int.Parse(row[0].ToString());
        }
    }
    e.ChildId = ++max;
}

    public partial class Form1 : Form
    {
        public class VM
        {
            public string Text
            {
                get; set;
            }
            public DateTime Start
            {
                get; set;
            }
            public DateTime End
            {
                get; set;
            }
        }

        public Form1()
        {
            InitializeComponent();

            var ViewModel = new VM[]
            {
                new VM()
                {
                    Text = "CrashTest",
                    Start = new DateTime(2021, 11, 3, 10, 0, 0),
                    End = new DateTime( 2021, 11, 3, 23, 0, 0 )  //crash
                    //End = new DateTime( 2021, 11, 3, 22, 0, 0 )  //No crash
                },
            };

            radGanttView1.GanttViewElement.GraphicalViewElement.OnePixelTime = new TimeSpan( 0, 1, 0 );
            radGanttView1.GanttViewElement.GraphicalViewElement.TimelineStart = ViewModel.Min( T => T.Start );
            radGanttView1.GanttViewElement.GraphicalViewElement.TimelineEnd = ViewModel.Max( T => T.End );
            radGanttView1.GanttViewElement.GraphicalViewElement.TimelineRange = TimeRange.Day;

            radGanttView1.GanttViewElement.ChildMember = "Text";
            radGanttView1.GanttViewElement.TitleMember = "Text";
            radGanttView1.GanttViewElement.StartMember = "Start";
            radGanttView1.GanttViewElement.EndMember = "End";

            radGanttView1.DataSource = ViewModel;
        }
    }

  radGanttView1.GanttViewElement.GraphicalViewElement.TimelineEnd = ViewModel.Max( T => T.End.AddHours(1));