Use as follows
public static List<string> _getContacts(int contactID)
{
List<string> val = new List<string>();
string val1 = "ABC";
string val2 = "DEF";
val.Add(val1);
val.Add(val2);
return val;
}
Retrieve data as follows
List<string> VAL = _getContacts(contactID);
Now you can use any element using index,. i.e., VAL[0],VAL[1]