DropDownList MouseWheel Behavior in C# Outlook VSTO Add-in

Hi Hristo,

Thank you for replying.

I downloaded the project you attached and tried your setup. It seems the issue still persist on my side. I also tried to set the static AllowAnimations property to false on my setup and the actual project, but the issue is not resolved. Does this have something to do with the telerik version?

I attached the screenshot of the version of my setup here.

Hi Hristo,

Before posting to Telerik Forums our QA team verified that the issue persist in their machine. 

Thank you for that. I guess the only option and work around we could do is to use DataGridView instead of Telerik RadGridView.

Regards,

Reed

I'm experiencing the exact behavior as the original poster. The mouse wheel causes scrolling to jump to the end of the list or to the top of the list when using the RadDropDownList, as well as the RadCheckedDropDownList, within an Office add-in. Was there any solution found for this issue?

Or is there a way to override the mouse wheel event for the dropdownlist element and simulate it in code?

Hello, David,   

Please note that as my colleague, Hristo, previously noted, COM/ActiveX projects and Outlook add-ins are having a different application life-cycle and message loop compared to a standard .NET application. In such scenarios it is possible to observe certain differences compared to a standard .NET project. Please note that we do not test our controls in such an environment and we do not guarantee normal work of the controls.

Have you tried the suggested solution with disabling the animation? Is the scrolling problem still reproducible?

According to the provided information, I am not sure whether you use the drop down list in RadGridView as an editor or as a separate control. However, in both cases you may use a similar approach for preventing the mouse wheel behavior.

RadGridView uses a RadDropDownListEditor for the combo columns. In order to disable scrolling the items in the popup, it is necessary to return true in the DropDownPopupForm.OnMouseWheel event. However, you will still be able to scroll the editable part in RadDropDownList. This can be stopped by overriding the RadDropDownListEditorElement.OnMouseWheel event and leaving the method empty. Then replace the default editor with the custom one in the EditorRequired event: https://docs.telerik.com/devtools/winforms/controls/gridview/editors/using-custom-editors

 public class CustomRadDropDownListEditor : RadDropDownListEditor
        {
            protected override RadElement CreateEditorElement()
            {
                return new CustomRadDropDownListEditorElement();
            }
        }

        public class CustomRadDropDownListEditorElement : RadDropDownListEditorElement
        {
            protected override RadPopupControlBase CreatePopupForm()
            {
                this.Popup = new CustomDropDownPopupForm(this);
                return Popup;
            }
            protected override void OnMouseWheel(MouseEventArgs e)
            {
 
            }
        }

        public class CustomDropDownPopupForm : DropDownPopupForm
        { 
            public CustomDropDownPopupForm(RadDropDownListElement ownerDropDownListElement) 
                : base(ownerDropDownListElement)
            {
            }

            public override bool OnMouseWheel(Control target, int delta)
            {
                return true;
            }
        }

For RadDropDownList, you can stop the default mouse wheel logic and implement your own as follows:

        public class CustomDropDownList : RadDropDownList
        {
            public override string ThemeClassName
            {
                get
                {
                    return typeof(RadDropDownList).FullName;
                }
            }

            protected override RadDropDownListElement CreateDropDownListElement()
            {
                return new CustomRadDropDownListElement();
            }
        }

        public class CustomRadDropDownListElement : RadDropDownListElement
        {
            protected override Type ThemeEffectiveType
            {
                get
                {
                    return typeof(RadDropDownListElement);
                }
            }

            protected override void OnMouseWheel(MouseEventArgs e)
            { 
            }

            protected override RadPopupControlBase CreatePopupForm()
            {
                this.Popup = new CustomDropDownPopupForm(this);
                return Popup;
            }
        }

        public class CustomDropDownPopupForm : DropDownPopupForm
        {
            public CustomDropDownPopupForm(RadDropDownListElement ownerDropDownListElement) : base(ownerDropDownListElement)
            {
            }

            public override bool OnMouseWheel(Control target, int delta)
            {
                return true;
            }
        }

If you are still experiencing any further difficulties, feel free to submit a support ticket from your account and provide a sample project demonstrating the undesired behavior hat you are facing. Thus, we would be able to make an adequate analysis of the precise case and provide further assistance. Thank you in advance.

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik

Hi Dess,

Thanks for your reply. I did try disabling the animation, but that didn't help. I finally pin-pointed the issue and have implemented a workaround until this issue can be fixed. It seems the OnMouseWheel event is being fired 3x for each mouse wheel delta turn event the mouse driver sends. So, if the mouse driver sends three deltas per notch, then each delta event is in turn multiplied by 3, thus raising a total of 9 OnMouseWheel events in rapid succession, causing the list to jump much further than it should. My solution was to reduce these back down to one event that gets passed-through per three events that are actually raised. Here is my code which does that, and I have attached a screenshot of all the classes used, similar to your examples above:

class TwDropDownPopupForm : DropDownPopupForm
{
private const int EventsPerDelta = 3;
private int eventCounter = 0;

public TwDropDownPopupForm(RadDropDownListElement ownerDropDownListElement) : base(ownerDropDownListElement)
{
}

/* 
* This override is necessary because of a mouse wheel scrolling issue with this Telerik element
* within an Office add-in host environment. The issue is that three OnMouseWheel events are
* fired in rapid succession per mouse wheel notch (delta). So, if the mouse driver raises three
* mouse wheel deltas, then each is multiplied by three events making a total of 9 OnMouseWheel 
* events being fired in rapid succession. The code below will reduce it back down to just one
* event that gets passed-through per three that are raised.
*/
public override bool OnMouseWheel(Control target, int delta)
{
if (++eventCounter / EventsPerDelta == 1)
{
eventCounter = 0;
return base.OnMouseWheel(target, delta); ;
}
return true;
}
}

Hello, David,   

I am glad that you have found a suitable solution for your scenario.

The different environment (Office Add-in) doesn't guarantee that the same number of MouseWheel messages will be received in RadDropDownList. Hence, the obtained behavior.

We already have a similar issue logged in our logged it in our feedback portal. You can track its progress, subscribe for status changes and add your comments on the following link  : https://feedback.telerik.com/winforms/1370581-fix-raddropdownlist-scrolling-with-the-mousewheel-or-down-arrow-key-jumps-from-the-first-to-the-last-item-in-word-add-in-when-the-popup-is-opened 

Should you have further questions please let me know.

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik