Drop-down values getting populating blank,based on deselection of Multi-select values of another dropdown values(when ever all values deselect).

Hi ,

i have a three drop down like A,B,C into our application.

First 'A' drop-down having set of fields, 'B' dropdown having set of fields so based on deselection of all values of drop-down B, C drop-down value should appear based on selected values of 'A' drop-down selected value.(but i'm getting values into debugging variable into backend but not getting populating on frontend ,drop-down values showing blank)

(Based on deselection of A drop down, third C drop-down value has to be populated by default values based on condition.)

please let me know more clarification.

quick reply should be appreciated.