Unable to select value from dropdown list with popop render out of Object Tree

Hi, 

I've add step to perform action, but it still doesn't work

- Below is the code:

function cboSelectWPF(inventoryType, value)
{   
  switch (inventoryType) {
    case DEFAULT_BEAM:     combobox = ddDefaultBeam ; break;
    case DEFAULT_SHEET:    combobox = ddDefaultSheet ; break;
    case BOTTOM_PLATE:     combobox = ddBottomPlate ; break;
    case SPACING_BEAMS:    combobox = ddSpacingBeams ; break;
    case TOP_PLATE:        combobox = ddTopPlate ; break;
  }
  combobox.ClickItem(value);
}

combobox is dropdown list with object in the screenshot

- Here is the properties of dropdown object. Could you pls check?

--------------------

Also I tried another way by expanding the dropdown menu then selecting a value but it didn't work.

I see the drop down menu expanded but can't select a value.

here is the script that I used to expanded the dropdown, then select the value with Click() function

function cboSelectWPF(inventoryType)
{   
  switch (inventoryType) {
    case DEFAULT_BEAM:     combobox = ddDefaultBeam ; break;
    case DEFAULT_SHEET:    combobox = ddDefaultSheet ; break;
    case BOTTOM_PLATE:     combobox = ddBottomPlate ; break;
    case SPACING_BEAMS:    combobox = ddSpacingBeams ; break;
    case TOP_PLATE:        combobox = ddTopPlate ; break;
  }
  combobox.Click();
  aqUtils.Delay(1000);
  tb2x4.Click();
  }

  combobox.Click(): to expand the dropdown list

  tb2x4.Click(): select with the value 2x4 from dropdown list