获取用户从组合框中选择的特定数据库的表名

I am working in visual studio to get the database names in SQL server and in obtaining those I am successful.But now I want to fill a combobox with the tables names of a database that is selected by user from another combobox. Here is what I have tried so far when I run the application the combobox for table names is filled for the Database that I have mentioned in the query.But it should depend on the user that if he selects any database from combobox then the table names for that database should be populated in table names combobox. So the user must not mention explicitly the name of database in query.I am working in visual studio to get the databa