I have To build the web browser in C#.net. in that web browser,if i load any URL that browser should export the name and all values of dropdown controls which present in that particular web page which i load.pl help me to build this web browser.

there's already a web browser control provided in .net..
If all goes well i can suggest you a solution for your task..
1) create a form which has a webbrowser control
2) load the required url in webbrowser control
3) write a javascript which extracts values from all the dropdowns on any page
4) inject the javascript into the page so that it runs as soon as the page finishes loading in your webbrowser control
5) javascript returns the formatted data to your form which then enters it into database
......
lemme know if that makes sense.. i have the source code of a working example which i'd done a while ago