C1ComboBox - Open Dropdown with Focus

Here, we will test for the property values IsKeyboardFocused and IsKeyboardFocusWithin and if either of them is true then will open the DropDown.

void c1ComboBox_IsKeyboardFocusedChanged(object sender, DependencyPropertyChangedEventArgs e)  
{  
   UpdateFocus();  
}  
void c1ComboBox_IsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e)  
{  
   UpdateFocus();  
}  
private void UpdateFocus()  
{  
   this.Dispatcher.BeginInvoke(new Action(delegate  
   {  
      // handle both properties, as ComboBox is complicated control, can have different combination of this properties  
      if (c1ComboBox.IsKeyboardFocused || c1ComboBox.IsKeyboardFocusWithin)  
      {  
        c1ComboBox.IsDropDownOpen = true;  
      }  
      else  
      {  
        c1ComboBox.IsDropDownOpen = false;  
      }  
  }));  
}