Hi MMarinich, This could be possibly because of a bug in v2.0.5.0. I have created a sample as per your update in v2.1.0.9, and see that the ComboBoxAdv behaves as expected when its Text or TextBox.Text properties are set to empty strings. Please refer to the test sample attached here. We strongly recommend you to upgrade to v2.1.0.9, and let me know if you continue to experience this problem in v2.1.0.9. We appreciate your cooperation. Regards, Guru Patwal Syncfusion, Inc.