************** Exception Text **************
System.InvalidOperationException: Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
   at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
   at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
   at System.Windows.Forms.Control.Invoke(Delegate method)
   at Telerik.WinControls.UIAutomation.RadControlBaseRootUIAutomationProvider`1.get_BoundingRectangle()
   at Telerik.WinControls.UIAutomation.Window.RadFormUIAutomationProvider.Form_Resize(Object sender, EventArgs e)
   at System.Windows.Forms.Control.OnResize(EventArgs e)
   at System.Windows.Forms.Form.OnResize(EventArgs e)
   at System.Windows.Forms.Control.OnSizeChanged(EventArgs e)
   at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height, Int32 clientWidth, Int32 clientHeight)
   at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height)
   at System.Windows.Forms.Control.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
   at System.Windows.Forms.Form.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
   at Telerik.WinControls.UI.RadFormControlBase.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
   at System.Windows.Forms.Control.SetBounds(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
   at System.Windows.Forms.Control.set_Size(Size value)
   at Telerik.WinControls.RadMessageBoxForm.SetSizeAndLocations()
   at Telerik.WinControls.RadMessageBoxForm.SetLabelTextAndSize(String text)
   at Telerik.WinControls.RadMessageBoxForm.set_MessageText(String value)
   at Telerik.WinControls.RadMessageBox.ShowCore(IWin32Window owner, String text, String caption, MessageBoxButtons buttons, Bitmap icon, MessageBoxDefaultButton defaultButton, RightToLeft rightToLeft, String detailsText)
   at dummyReader.FormMain.radButtonLogin_Click(Object sender, EventArgs e)
   at System.EventHandler.Invoke(Object sender, EventArgs e)
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at Telerik.WinControls.RadControl.OnClick(EventArgs e)
   at Telerik.WinControls.UI.RadButtonBase.buttonElement_Click(Object sender, EventArgs e)
   at Telerik.WinControls.RadElement.OnClick(EventArgs e)
   at Telerik.WinControls.UI.RadButtonItem.OnClick(EventArgs e)
   at Telerik.WinControls.UI.RadButtonElement.OnClick(EventArgs e)
   at Telerik.WinControls.RadElement.DoClick(EventArgs e)
   at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
   at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
   at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
   at Telerik.WinControls.RadElement.DoMouseUp(MouseEventArgs e)
   at Telerik.WinControls.ComponentInputBehavior.OnMouseUp(MouseEventArgs e)
   at Telerik.WinControls.RadControl.OnMouseUp(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at Telerik.WinControls.RadControl.WndProc(Message& m)
   at Telerik.WinControls.UI.RadButton.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

 

 

The arrow button click does not work as expected in the latest release version. This is a regression in our latest 2026.2.702 release, where the AllowedClickButtons property is not initialized correctly. We are working on a fix! Please subscribe to this item, and you will receive an email notification when we introduce the fix.

In the meantime, you can apply the following workaround:

Or use v.2026.2.520, where the arrow button functions as usual.

We appreciate your patience and apologize for the inconvenience this issue may have caused. 

This exception is a result of changes in the Current property of the IEnumerator interface. With the lastest version, if the current item is undefined it will throw an exception if we try to access it with the Current property, while in the older version, it will return null.

This item is migrated to the Telerik Document Processing portal: 
http://feedback.telerik.com/Project/184/Feedback/Details/190124 
Please use the new item for commenting, voting and subscribing instead of this one.

Use attached to reproduce.

Workaround:

- Use RadForm it explicitly handles the controls scaling. 
- Make sure that the following of the user controls are set like this:

this.AutoScaleDimensions = new System.Drawing.SizeF(96F, 96F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Dpi;