Fetch values from gridview in dropdownlist using c#

Question

hello everyone;

i want to fetch values of "patient reg code" from gridview of "clinic patient registration" and place in the dropdownlist of "patient reg code" of "opd info". remember "clinic patient registration" and "opd info" are two forms in asp.net." and "patient reg code" is a source values of gridview. i am sending screen shot of my problem . you can take help from this.

regards
sumaira