Error is received when click on button. Reproduced randomly on different machines.

Since 2025 Q2 you'll get this error message when you try to open a flyout on a control that is not a Form. This does not happen with 2025 Q1.

Might be related: https://feedback.telerik.com/winforms/1688619-radform-clientsize-on-inherited-radform-is-broken

However, this time I have no patch / workaround. I have not the time to investigage deeper at the moment, so update to Q2 not possible for me at the moment.

 This issue starts happening as of Q2 (2025.2.520) version.

Workaround: override SetClientSizeCore() inside of inherited RadForm

public partial class RadForm2 : RadForm1
{
    protected override void SetClientSizeCore(int x, int y)
    {
        base.SetClientSizeCore(x, y);

        if ((!this.IsLoaded || !this.IsHandleCreated) &&
            this.IsInitialized)
        {
            MethodInfo mi = typeof(Form).GetMethod("SetClientSizeCore", BindingFlags.NonPublic | BindingFlags.Instance);
            if (mi != null)
            {
                IntPtr ptr = mi.MethodHandle.GetFunctionPointer();
                Action<int, int> baseSetClientSizeCore = (Action<int, int>)Activator.CreateInstance(
                    typeof(Action<int, int>), this, ptr);

                baseSetClientSizeCore.Invoke(x, y);
            }
        }
    }
}

Add a call to "OnImageLoaded" to "RadPictureBoxelement.PasteImage()" method or create an event like "ImagePasted" ot be able to tract an image change at this point.

For me I solved this via an Harmony patch that adds a call to OnImageLoaded() on PasteImage()  long time ago. Not really elegant, but I'm a noob in patching with Harmony.

Just want to leave it here for anyone that want ot use this solution too or for Telerik to implement a native way to expose an image change via PasteImage.

[HarmonyPatch(typeof(RadPictureBoxElement))]
[HarmonyPatch("PasteImage")]
public class RadPictureBoxElement_PasteImageFixes
{
    private static readonly Dictionary<RadPictureBoxElement, Image> images = [];

    public static void Prefix(object __instance)
    {
        if (__instance is RadPictureBoxElement pb)
        {
            // Remember our image
            images.Remove(pb);
            images.Add(pb, pb.Image);
        }
    }

    public static void Postfix(object __instance)
    {
        if (__instance is RadPictureBoxElement pb && images.TryGetValue(pb, out var image) && pb.Image != image)
        {
            // Remove first to avoid conflicts on error
            images.Remove(pb);

            // Call "OnImageLoaded"
            var method = typeof(RadPictureBoxElement).GetMethod("OnImageLoaded", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
            method.Invoke(pb, null);
        }
    }
}

Steps to recreate:

• click on the button on the top row
• press the down key on the keyboard
• Press Space key to select new button, the button on the top row is clicked

When Telerik UI for WinForms / WPF extensions are installed, Visual Studio is unresponsive for a couple of minutes after a solution is loaded. During that time, "Updating source control status…" is shown.

Workarounds:

• Disable Telerik UI for WinForms / WPF extensions.
• Checkout the solution file.

Provide an AI assistant for code generation with the Telerik UI for WinForms controls. 

Such as Telerik Blazor AI Coding Assistant

 Upgrade Project Wizard should use 2025.2.520.48 version in .NET Framework 4.8 project.

Add support for the RadRibbonBars to have their items merged while in MDI mode.

Steps to Reproduce:

1. Create a new WinForms application targeting .NET 9.

2. Add a RadStatusStrip to the main form.

3. Run the application.

4. Snap the form to the left or right edge of the screen (using Windows Snap).

5. Minimize the form.

6. Restore the form.

Expected Behavior:
The form should maintain its original size and remain fully visible on screen after being restored.

Actual Behavior:
Every time the form is minimized and restored, it increases in height. After a few cycles, the bottom part of the form — including the RadStatusStrip — becomes hidden behind the Windows taskbar (Start menu).

Additional Info:

• The issue only occurs when a RadStatusStrip is added to the form.

• The issue does not occur when using a standard StatusStrip from WinForms.

• The problem occurs consistently and can be reproduced easily.

• Tested both in debug mode and with a compiled executable.

Attachments:

• Screenshots (before and after restore).

• Sample reproduction project (if needed).

  This is only repeated in windows 10

   

When enabling AutoSize on all RadTextBoxControl elements on a Form and the Form has its AutoSize porperty set to True, then the size of the TextBoxElement inside the TextBox autosizes wrong. See the pictures. This happens at runtime and under specific conditions also at design time.

If you change Form.AutoSize to False OR at least ONE RadTextBoxControl to AutoSize = False then everything works as normal. But if ALL RadTextBoxControl has AutoSize to True and The Form.AutoSize is True, then this happens.

Office 2019:

Windows 11 Compact: