System.Data.SqlClient.SqlException: 'Cannot open backup device 'C:\DatabaseBackupFile\database.bak'. Operating system error

Question

I hosted an asp.net core 2.1 web application on an online server, now I am trying to get database backup using the user interface, when I put the online database connection string, the below error show,

System.Data.SqlClient.SqlException: 'Cannot open backup device 'C:\DatabaseBackupFile\database.bak'. Operating system error 3(The system cannot find the path specified.). BACKUP DATABASE is terminating abnormally.'

But when I use the local database connection string there is no error, I can get a successful database backup and save it to my local drive path.

Here is my Code:

        public IActionResult TakeDatabaseBackup()
    {
        try
        {
           //  var connectionString = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=DatabaseName;Data Source=SQLEXPRESS";

           var connectionString = "Data Source=SQLOnlineWebServer.com;Initial Catalog=DatabaseName;User Id=DatabaseUserName;Password=123456789";

            var backupFolder = System.IO.Directory.CreateDirectory("C:/DatabaseBackupFile/").ToString();

            var sqlConStrBuilder = new SqlConnectionStringBuilder(connectionString);
            var backupFileName = String.Format("{0}{1}-{2}.bak",
                backupFolder, sqlConStrBuilder.InitialCatalog,
                GetLocalDateTime().ToString("MM-dd-yyyy-hh-mm-tt"));
            using (var connection = new SqlConnection(sqlConStrBuilder.ConnectionString))
            {
                var query = String.Format("BACKUP DATABASE {0} TO DISK='{1}'",
                    sqlConStrBuilder.InitialCatalog, backupFileName);
                using (var command = new SqlCommand(query, connection))
                {
                    connection.Open();
                    command.ExecuteNonQuery();
                }
            }
            return Json(new { type = "success" });
        }
        catch
        {
            return Json(new { type = "error" });
        }
    }

Please help how to solve this error

System.Data.SqlClient.SqlException: 'Cannot open backup device 'C:\DatabaseBackupFile\databaseName.bak'. Operating system error 3(The system cannot find the path specified.). BACKUP DATABASE is terminating abnormally.'