• $select                 Specify properties to return
• $filter                   Constrain records to return (WHERE)
• $orderby              Sort the results
• $top                      Limit the number of results returned
• $skip                     Skip records before returning results (paging)

$filter=CreditLimit ge 9000&$orderby=CreditLimit desc

public method CreateNewOrder, int
    required in aOrder, @Order
    required in aOrderItems, @List<OrderItem>
proc
    ;;Validate inbound data (we're not a controller so we can't use ModelState!)

    if (aOrderItems.Count<1)
        throw new ApplicationException("No items were provided!")

    ;TODO: Need more data validation
    ;;Customer ID needs to be valid
    ;;Item ID's need to be valid
    ;;And more

    ;;Allocate the next available order number to the new order
    disposable data keyFactory = (@IPrimaryKeyFactory)mServiceProvider.GetService(^typeof(IPrimaryKeyFactory))
    keyFactory.AssignPrimaryKey(aOrder)

    ;;Propagate the new order number to the order items, and polulate line item numbers
    data item, @OrderItem
    data itemNumber = 0
    foreach item in aOrderItems
    begin
        item.OrderNumber = aOrder.OrderNumber
        item.ItemNumber = (itemNumber+=1)
    end

    ;;Save the new order
    mDbContext.Orders.Add(aOrder)
    mDbContext.OrderItems.AddRange(aOrderItems)
    mDbContext.SaveChanges(keyFactory)

    ;TODO: What happens if something fails?

    mreturn aOrder.OrderNumber

endmethod

{
	"aOrder":{
		"CustomerNumber": 8,
		"PlacedBy": "Max Henry",
		"CustomerReference": "NEWORD1",
		"PaymentTermsCode": "04",
		"DateOrdered": "2018-03-07T00:00:00Z"
	},
	"aOrderItems": [
		{
			"ItemOrdered": 20,
			"QuantityOrdered": 25,
			"UnitPrice": 1.49
		},
		{
			"ItemOrdered": 5,
			"QuantityOrdered": 25,
			"UnitPrice": 1.49
		}
	]
}

data uri, string, "https://harmonycoreapp.azurewebsites.net/odata/Customers(1)?$expand=REL_Orders"
data caFile, string, "C:\path\to\TrustedRootCA.pem"
data responseString, string
data errorText, string
data sendHeaders, [#]string, new string[#] {"Host: harmonycoreapp.azurewebsites.net"}
data recvHeaders, [#]string
data httpError, int
httpError = %http_get(uri,5,responseString,errorText,sendHeaders,recvHeaders,,,,,caFile,,"1.0")

1. Notice that we're explicitly using HTTP 1.0 for this call. This is because if we use HTTP 1.1 the WebAPI service will take advantage of an HTTP 1.1 feature called Chunked Transfer Encoding. which isn't currently supported by the Synergy HTTP API. Support will be added in Synergy 11.
2. This code doesn't deserialize the response to a collection of objects like Jeff's code does. Here the responseString variable is literally a string containing the JSON response from the service, but you can use Jeff's very cool traditional Synergy JSON Parser class which is available in the Harmony Core source code repository.

I feel I should clarify a few aspects of this thread.  The Symphony Framework has been developed over the last 8 years and provides the ability to expose Synergy data and logic to a wide number of client architectures.  These include in-process WPF desktop applications, enhancements to UI Toolkit programs and via a number of network endpoints including TCP, HTTP(s) and Microsoft’s Service Bus Relay.  Symphony Conductor is at the core of the Symphony Framework providing data mapping between Synergy proprietary data types and industry standard data types.  Symphony Harmony provides data access and remote logic execution capabilities that fully utilize the Symphony Conductor data models and the Synergy Select class.  Symphony Bridge is a Windows Service that provides self-hosted network endpoints that allow access through Symphony Harmony to Synergy ISAM data and existing application logic.  Symphony Bridge “out-of-the-box” provides network endpoints for TCP and HTTP(s) as well as Service Bus Relay.  It has, for some 3 years, provided a fully functional, standard RESTful API to allow access to the same Synergy ISAM data and existing application logic using standard URI syntax.  You can perform all the standard tasks (selecting data with full filtering capabilities, updating or creating data, etc.) using simple URI syntax.

Harmony Core is not an extension or evolution of the Symphony Framework.  Harmony Core has taken some of the ideas of the Symphony Framework and a small number of code concepts but is a complete rewrite.  Harmony Core is not compatible with anything currently available within the Symphony Framework.

The RESTful endpoint provided by Symphony Bridge provides powerful data access to individual ISAM files by marshalling the URI query to the Synergy select class and optimizing data access by performing sparse select queries.  This same endpoint provides seamless access to existing application logic using the concept of stored procedures without having to extend or write additional controller code.  Symphony Bridge protects the execution of this existing logic by using AppDomain’s to ensure that common/global data, hard-wired channel numbers and all none thread-safe code is completely isolated.  Stored procedures can be used to return complex, multi-layered collections of data objects or process complex inbound structures to store data into any supported database.

With nearly 30 years’ experience of working with Synergy ISAM files I am acutely aware of the problems encountered when trying to “join” files together and attempting to present them as a “relational” data model. Most applications today already have the complex logic required to “join” related files together to “load” for example a sales order.  Through Symphony Bridge you can expose the sales order object as a collection of Symphony Data Objects and provide access using your tried and tested logic.  This prevents to need to try to construct a complex URI query on each individual client to retrieve the same data.  The code is in one place – the server. 

Symphony Harmony also allows you to define Composite fields.  These enable you to define read-only non-repository fields that can return joined or calculated data.  When extending the structure based data object with a composite field you declare the fields that Symphony Harmony must also load to enable correct processing of your composite field.  For example you could define a composite field of SupplierName on your Order Header.  The SupplierName field requires the SupplierCode field to be loaded from the order header file.  If you select records from your order header file and include the SupplierName field, Symphony Harmony knows it must also read the SupplierCode field from the data file before executing the code within the SupplierName property where you load and return the required supplier information.

Harmony Core is an alternative to the Symphony Framework with, as presented at DevPartner 2018, less functionality.  Symphony Framework is now owned and developed by RCP Consultants.