Decision router

Routes each record to one of several branches. A C# script returns a route name for the record; the record is sent to the outgoing connections whose route id equals that name. Use it for if/else and switch-like branching.

Pins

Pin	Kind	Types	Description
Input	input	any	Records to route.
Output	output	same as input	The unchanged input record. Draw one connection per branch from this pin and set the connection's route id (connection properties) to the route name.

Configuration

Field	Type	Default	Description
Condition	string (C# code editor)	generated template	C# code containing the method GetRoute (see below).

The Condition script

The script is the body of a class; it must contain exactly this method:

public string GetRoute(IMetaData metaDataInstance, IViaType inputDataInstance)
{
    var metaData = (MyFlowNamespace.FlowMetaData)metaDataInstance;
    var inputData = (MyFlowNamespace.Order)inputDataInstance;
    if (inputData.Amount > 1000) return "Large";
    return "Small";
}

• The returned string is the route name. It is compared exactly (case-sensitive) with the route id of each outgoing connection.
• The template generated by the designer casts the metadata to the flow's FlowMetaData and the input to the input connection's type; adjust the cast when the input type changes.
• using statements can be written anywhere in the script; they are moved to the top. Common namespaces (System, System.Linq, System.Collections.Generic, Viaducta.TypeSystem, Viaducta.TypeSystem.Metadata, Viaducta.Plugin.Design, the flow namespace, ...) are already imported. NuGet packages of the flow can be used.
• The property Services (IFlowService) is available in the script for logging, flow properties, etc.

Behaviour

• For each record a new script instance is created, GetRoute is called and the result is stored as the record's route id; the record is then sent to Output.
• Delivery from Output:
  • connections with a route id receive the record only when the route id equals the returned name;
  • connections without a route id receive every record whose type matches (they are not an "else" branch).
• If no connection matches the returned name (for example the default template's empty string), the record is dropped silently.
• An exception thrown by the script fails the record (normal error handling of the flow applies).
• Without a script the designer shows a "no condition" indicator and a warning; the default template returns an empty string.

Notes

• To build an "else" branch, return an explicit name for it (for example "Other") and set that route id on the connection; do not leave a connection without a route id.
• The route id is stored on the record object itself. If a downstream component passes the same record on, the route id travels with it and can affect other route-id connections later in the flow.
• The script runs on every record; keep it fast and free of side effects.

Example

Script returns "Large" or "Small":

Http listener → Decision router → (route id Large) Approval flow ; (route id Small) Database writer