Unity DropDown Cause crash

Unity 2019.4.1.

I had tried to modify the dropdown size to auto fit with phones.

but seems it cause the app crash?

        JobDropDown.ClearOptions();
        //dropdown length 4 items
        JobDropDown.template.sizeDelta = new Vector2(0, DropDownWidth);//(int)(Screen.height * 0.28);
        JobContent.sizeDelta = new Vector2(0, DropDownItemWidth); //(int)(Screen.height * 0.07);
        JobItem.sizeDelta = new Vector2(0, DropDownItemWidth);
        JobLabel.sizeDelta = new Vector2(0, DropDownItemWidth);
        for (int i = 0; i < (int)JobName.Max; i++)
        {
            JobDropDown.options.Add(new Dropdown.OptionData
            {
                text = ((JobName)i).ToString()

            });
            Debug.Log("add " + ((JobName)i).ToString());
            
        }

is it the correct way to deal with dropdown?

Every time I click the dropdown it definitely lag for few seconds,

and the result is crash or show the dropdownlist half to half.

Items is surely add to the dropdownlist.