Back up Database online web site...

// You'll need to read a little bit about how this query works.
// It's a lot of different ways of doing this. This is an example:
string sql = "BACKUP DATABASE [SQL Database] TO DISK = 'D:\SQLDatabase.bak'";
SqlConnection cn = new SqlConnection("connectionstring");
SqlCommand cmd = new SqlCommand(sql, cn);
cn.Open();
cmd.ExecuteNonQuery();
cn.Close();