I am using sql server management studio 2005 express i have created my own database in it,but i want to add that databse to my project i dnt know how, i have added database to my project by right clicking on app_data and add new item but it is not my database please help me on this.THANKS.

 Either add a new Database in ur project as u've already done and create tables and enter data through visual studio database explorer (Double click on dataBaseName.mdf )

If you want to add the database you've created in sql server express than right click on databse name in sql server management studio and select detach 

Copy the databaseName.mdf and  databaseName_Log files from sql server installation directory (usually C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data)  to desktop

Now right click on solution explorer in Visual studio > select Add existing item > browse to databsename.mdf on desktop > click ok 

Done 

 yes it worked thanks.