我该如何解决此组合框故障？

Question

我创建了自己的组合框，并进行了一些小的更改。但是我在下拉列表中遇到错误。
我将combobox.DroppedDown = True设置为
每当我打开新表单时，每种表单都会发生这种情况。
组合框代码为

Public Class MainComboxex

Inherits ComboBox

Private Sub MainComboBoxEx_Enter(sender As Object, e As EventArgs) Handles Me.Enter
    Me.BackColor = Color.FromArgb(247, 180, 65)
End Sub

Private Sub MainComboBoxEx_Leave(sender As Object, e As EventArgs) Handles Me.Leave
    Me.BackColor = Color.White
End Sub

'Private Sub InitializeComponent()
'    Me.SuspendLayout()
'    Me.ResumeLayout(False)
'End Sub

Private Sub MainComboxex_KeyPress(sender As Object, e As KeyPressEventArgs) Handles Me.KeyPress
    Try
        If Char.IsControl(e.KeyChar) = False Then
            e.Handled = AutoFillCombo(Me, e.KeyChar.ToString)
        End If
    Catch ex As Exception
        MsgBox(ex.ToString)
    End Try
End Sub
End Class

但是它的行为是这样的。

再次单击组合框后，它将正常工作，如下所示。