how toshow the the data in text box

Amu ,

I want you to do it yourself . Below is algorithm . Read it step by step . Do the thing and will result into what you want.
I hope you are using some other language also for framework(VB.net Or C# ETC)

Note : Please replace framework language "{Your FW Lang}" in below steps with language you are using for FW.

Algorithm
1) Create one public method in your language to connect the database (Connection object)
2) Open "WWW.GOOGLE.COM" and search for "How to connect database in "{Your FW Lang}"
3) Modified connection string in the code you have found in above step so that it will take database name from use selection
4) Call this method on click event of "Database Selection Drop Down Box"
5) It will create connection object which will have database connection
6) Create one method to populate branch no taking source as database table. Use connection object created in above step
7) Call this method along with step no 4
8) Create one more method with will run query to find branch name from branch no. Use connection object created in step#3
9) Call this method on click event of "Branch No Selection Drop Down Box" and display result on to text box

Hope this will help if yes then vote and accept the answer otherwise revert back with your queries
--RD