Last Updated: 06 Jun 2022 09:33 by ADMIN
Release R2 2022 (LIB 2022.2.606)
Created on: 13 May 2022 06:54
Category: WaitingBar
Type: Bug Report
RadWaitingBar: NullreferenceException on StartWaiting()

Use the attached sample project and click the button:

   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)

                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
                    return typeof(RadWaitingBar).FullName;


Dess | Tech Support Engineer, Principal
Posted on: 25 May 2022 08:48

Hi, Marco,

Please have in mind that the fix will be introduced in the upcoming service pack - R2 2022 SP1 which is scheduled for the middle of June. 

In case you are experiencing any further difficulties, I would recommend you to submit a support ticket from your Telerik account with detailed information about the precise case. Thus, we will be able to investigate the precise case and provide further assistance. Thank you in advance.

Dess | Tech Support Engineer, Principal
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Posted on: 24 May 2022 08:12

I'm using version 2022.2.510 and I still have this bug.

I'm showing the RadWaitingBar on a Telerik.WinControls.UI.Docking.DocumentWindow


I fixed with solution proposed in this thread, but I have a regression on a fix I asked 1 month ago:

The top bar is included in the waiting bar background when associated control is a Form