C# - How to Prevent Mousewheel-Scrolling in My Combobox

How to disable mousewheel for one control i.e. Combo Box?

Add an event handler to your code

private void anycontrol_MouseEnter(object sender, System.EventArgs e) 
{
    var senderControl = sender as System.Windows.Forms.Control;
    if(senderControl==null)
        return;
    senderControl.Focus();
}

And assign it to any controls you want your focus to be applied automatically.

somePanel.MouseEnter += new System.EventHandler(anycontrol_MouseEnter);
//or this way
somePanel.MouseEnter += anycontrol_MouseEnter;
someComboBox.MouseEnter += anycontrol_MouseEnter;

edit:

Including the details you provided, I'd do it this way:

bool AllowUsersScrolling;
private void usersCombobox_MouseLeave(object sender, System.EventArgs e) 
{
    AllowUsersScrolling = false;
}
private void usersCombobox_MouseEnter(object sender, System.EventArgs e) 
{
    AllowUsersScrolling = true;
}
private void usersCombobox_MouseWheel(object sender, MouseEventArgs e)
{
    if(!AllowUsersScrolling)
        ((HandledMouseEventArgs)e).Handled = true;
}

And attach those handlers to your control's events respectively.

How to prevent Mouse Scroll in ToolStripComboBox?

The ToolStripComboBox helpfully exposes its underlying ComboBox control in its aptly named ComboBox property. This allows us to access its properties, methods, and events that were not been wrapped into the ToolStripComboBox.

And, as you probably know, the standard ComboBox control exposes a MouseWheel event that fires each time the mouse wheel is scrolled while the combo box has focus.

Putting these two things together, we can add a handler for the ToolStripComboBox control's underlying ComboBox control's MouseWheel event, and override its default behavior.

So, assuming you have a form that contains a ToolStrip and a ToolStripComboBox, you can use something like the following code:

public partial class Form1 : Form
{
   public Form1()
   {
      InitializeComponent();

      //Attach a handler for the MouseWheel event
      ToolStripComboBox1.ComboBox.MouseWheel += new MouseEventHandler(ToolStripComboBox_MouseWheel);
   }

   private void ToolStripComboBox_MouseWheel(object sender, MouseEventArgs e)
   {
      //Cast the MouseEventArgs to HandledMouseEventArgs
      HandledMouseEventArgs mwe = (HandledMouseEventArgs)e;

      //Indicate that this event was handled
      //(prevents the event from being sent to its parent control)
      mwe.Handled = true;
   }
}

Alternatively, of course, you could always subclass the existing ToolStripComboBox control and override its behavior there in the same way shown above.

How to keep ComboBox from scrolling? C#

combobox.MouseWheel += new MouseEventHandler(combobox_MouseWheel);

void combobox_MouseWheel(object sender, MouseEventArgs e)
{
    ((HandledMouseEventArgs)e).Handled = true;
}

Disable scrolling for mouse-over in ComboBox (WPF)

You could handle the RequestBringIntoView event for the ComboBoxItem containers:

<ComboBox>
    <ComboBox.ItemContainerStyle>
        <Style TargetType="ComboBoxItem">
            <EventSetter Event="RequestBringIntoView" Handler="ComboBox_RequestBringIntoView"/>
        </Style>
    </ComboBox.ItemContainerStyle>
</ComboBox>

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private void ComboBox_RequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
    e.Handled = true;
}

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