Add this code on App.config file
<connectionStrings>
<add connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\projecty bashi nawxoyy\Bashi Nawxoyy\Bashi Nawxoyy\db_file.accdb" name="connectionString"/>
</connectionStrings>
and call connection string on your .cs class
string conString = System.Configuration.ConfigurationManager.ConnectionStrings["connectionString"].ToString();
db_con = new OleDbConnection(conString);
Thanks & Regard
Sham :)