How to create a custom control

Kindly refer following links
http://msdn.microsoft.com/en-us/library/aa728786%28v=vs.71%29.aspx

Rajesh Patel
MCPD,MS
Brainbench (Asp.Net 4.0 and CSS 3.0)

Customer control means user control
Steps
1) Add .ascx file in use solution.
2) add the code u wish to display (drop down list and textbox) events also
3)register user control in page in which u want to used that control.
4)call that control in source and code behind

http://www.codeproject.com/Articles/521/Creating-Custom-Controls
http://msdn.microsoft.com/en-us/library/aa728786%28v=vs.71%29.aspx