Maybe the database is not being attached as Garment even though the file name is Garment.mdf. Modify your connection string to :'
string con = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\bin\Debug\Garment.mdf;Database=Garment;Integrated Security=True;Asynchronous Processing= True ;User Instance=True";
Take note of the Database keyword in the connection string.