Binding a combo box located on the multi-tab control which is on the user control to the data in the Access database.

Question

I am fairly new to (C#) programming. Hence the need for somebodies assistance.

I have created an application which derives data from the Access database and displays them on the different controls ( text boxes, combo-boxes, labels etc. ). Everything was working fine when I had just a main form and a multi- tab control. When I decided to change the design and introduced a split-container,  a tree-view one form (base-form) and a few user-controls I run into this problem whereby I couldn't get the data from the data base to display on the combo-box which was one of the tabs in a multi-tab control and multi-tab control was sitting on the user-control. 

Could any body suggest the best way to achieve this?

Thank you in advance.