Notice if you place the cursor in the TextBox on the http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/ComboBox/ComboBox.aspx page that you cannot type anything until one of the items in the drop down list is selected. This can be corrected by adding __" && this._optionListItems.length == 0"__ to the if statement below "prevent typing when there are no items in the list" on line 834 of the ComboBox.pre.js file:
```
// prevent typing when there are no items in the list
if (this.get_selectedIndex() == -1 && this.get_dropDownStyle() == Sys.Extended.UI.ComboBoxStyle.DropDownList && this._optionListItems.length == 0) {
this.get_textBoxControl().value = '';
e.preventDefault();
e.stopPropagation();
return false;
}
```
```
// prevent typing when there are no items in the list
if (this.get_selectedIndex() == -1 && this.get_dropDownStyle() == Sys.Extended.UI.ComboBoxStyle.DropDownList && this._optionListItems.length == 0) {
this.get_textBoxControl().value = '';
e.preventDefault();
e.stopPropagation();
return false;
}
```