at Telerik.WinControls.TelerikPaintHelper.GenerateSnapShotWithBitBlt(Control control)
   at Telerik.WinControls.UI.RadWaitingBar.AddBackgroundImageToAssociatedControlCoverPanel()
   at Telerik.WinControls.UI.RadWaitingBar.ShowCover()
   at Telerik.WinControls.UI.RadWaitingBar.StartWaiting()
   at TelerikWinFormsApp1.RadForm1.radButton1_Click(Object sender, EventArgs e) in C:\Projects\1564934_telerikwinformsapp1\TelerikWinFormsApp1\RadForm1.cs:line 31

        public class CustomWaitingBar : RadWaitingBar
        {
            protected override void AddBackgroundImageToAssociatedControlCoverPanel()
            {
                Size associatedControlSize = this.AssociatedControl.Size;
                if (associatedControlSize.Width <= 0 || associatedControlSize.Height <= 0)
                {
                    return;
                }

                Bitmap controlImage = new Bitmap(associatedControlSize.Width, associatedControlSize.Height);
                this.AssociatedControl.DrawToBitmap(controlImage, new Rectangle(Point.Empty, associatedControlSize));
                SolidBrush semiTransBrush = new SolidBrush(this.AssociatedControlCoverPanel.BackColor); // Color.FromArgb(128, 255, 255, 255) Default color
                Graphics g = Graphics.FromImage(controlImage);
                g.FillRectangle(semiTransBrush, new Rectangle(Point.Empty, controlImage.Size));
                this.AssociatedControlCoverPanel.BackgroundImage = controlImage;
            }

            public override string ThemeClassName
            {
                get
                {
                    return typeof(RadWaitingBar).FullName;
                }
            }
        }