Message: Object reference not set to an instance of an object.
Telerik.WinControls.UI.RadGridViewDragDropService.GetDragImageHint(ContentAlignment textAlignment, Bitmap hintImage, RectangleF textRectangle, Int32 hintImageWidth)
Telerik.WinControls.UI.ColumnChooserItem.GetDragHintCore()
Telerik.WinControls.RadItem.Telerik.WinControls.ISupportDrag.GetDragHint()
Telerik.WinControls.RadDragDropService.PrepareContext():80
Telerik.WinControls.RadDragDropService.HandleMouseMove(Point mousePos):40
Telerik.WinControls.UI.RadGridViewDragDropService.HandleMouseMove(Point mousePosition):13
Telerik.WinControls.RadDragDropService.Telerik.WinControls.IMessageListener.PreviewMessage(Message& msg):150
Telerik.WinControls.RadMessageFilter.NotifyGetMessageEvent(Message& msg):41
Telerik.WinControls.RadMessageFilter.GetMessageHookProc(Int32 code, IntPtr wParam, IntPtr lParam):36

            if (int.TryParse(txtCount.Text, out int count))
            {
                string textToSet=new string('A', count)+"END";
                txtSample.Text = textToSet;

                this.radTextBox1.MaxLength = textToSet.Length;
               
                this.Text = txtSample.Text.Length.ToString();
               
            }

            DataTable dt = new DataTable();
            dt.Columns.Add("Id", typeof(int));
            dt.Columns.Add("Title", typeof(string));
            dt.Columns.Add("Price", typeof(decimal));

            for (int i = 0; i < 10; i++)
            {
                dt.Rows.Add(i, "Row" + i, 0);
            }

            this.radGridView1.DataSource = dt;
            this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;

            GridViewSummaryItem summaryItem = new GridViewSummaryItem();
            summaryItem.Name = "Price";
            summaryItem.Aggregate = GridAggregateFunction.StDev;
            GridViewSummaryRowItem summaryRowItem = new GridViewSummaryRowItem();
            summaryRowItem.Add(summaryItem); 
            this.radGridView1.SummaryRowsBottom.Add(summaryRowItem);

public class MyCompositeDataFilterForm : CompositeDataFilterForm
{
    protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
    {
        if(keyData == Keys.Enter)
        {
            this.Controls[2] as RadButton).Focus();
             (this.Controls[2] as RadButton).PerformClick();
        }
        return base.ProcessCmdKey(ref msg, keyData);
    }
}

private void RadGridView1_CreateCompositeFilterDialog(object sender, GridViewCreateCompositeFilterDialogEventArgs e)
{
    var newForm = new MyCompositeDataFilterForm();
    e.Dialog = newForm;
}  

        static void Main(string[] args)
        {
            int i = 1;
            try
            {
                Stopwatch stopwatch = Stopwatch.StartNew();
                while (true)
                {
                    using (RadPdfViewer pdfViewer = new RadPdfViewer())
                    {

                    }
                    Console.WriteLine($"iteration {i}, elapsed seconds: {stopwatch.Elapsed.TotalSeconds}");
                    i++;
                }
            }
            catch (Exception e)
            {
                Console.WriteLine($"Exception occurred at iteration {i}");
                Console.WriteLine(e);
                Console.ReadLine();
            }
        }

System.Runtime.InteropServices.ExternalException (0x80004005): A generic error occurred in GDI+.
   at System.Drawing.Bitmap.GetHicon()
   at Telerik.WinControls.PdfViewer.MouseHandlers.PanHandler..ctor(MouseHandlersController controller, IFixedDocumentPresenter presenter)
   at Telerik.WinControls.PdfViewer.MouseHandlers.MouseHandlersController.BuildHandlers(IFixedDocumentPresenter presenter)
   at Telerik.WinControls.PdfViewer.MouseHandlers.MouseHandlersController..ctor(IFixedDocumentPresenter presenter)
   at Telerik.WinControls.UI.RadPdfViewerElement..ctor()
   at Telerik.WinControls.UI.RadPdfViewer.CreateViewerElement()
   at Telerik.WinControls.UI.RadPdfViewer.CreateChildItems(RadElement parent)
   at Telerik.WinControls.RadControl.Telerik.WinControls.IComponentTreeHandler.CreateChildItems(RadElement parent)
   at Telerik.WinControls.RadElementTree.InitializeRootElement()
   at Telerik.WinControls.RadControl.Construct()
   at Telerik.WinControls.RadControl..ctor()
   at Telerik.WinControls.UI.RadPdfViewer..ctor()

            GridPrintStyle style = new GridPrintStyle();
            style.PrintHierarchy = true;
            style.HierarchyIndent = 0;
            style.ChildViewPrintMode = ChildViewPrintMode.SelectViewToPrint;
            this.radGridView1.PrintStyle = style;

            this.radGridView1.PrintPreview();

private void RadRichTextEditor1_CommandExecuted(object sender, CommandExecutedEventArgs e)
{
    if (e.Command is PasteCommand)
    {             
        Application.DoEvents();

        bool cursorAtDocEnd = this.radRichTextEditor1.Document.CaretPosition.IsPositionAtDocumentEnd;
        if (cursorAtDocEnd)
        {
            MoveCaretCommand command = new MoveCaretCommand(this.radRichTextEditor1.RichTextBoxElement);
            command.Execute(MoveCaretDirections.Down);
        }
    }
}