Loading workflow definitions from JSON or YAML

Install the WorkflowCore.DSL package from nuget and call AddWorkflowDSL on your service collection. Then grab the DefinitionLoader from the IoC container and call the .LoadDefinition method

using WorkflowCore.Interface;
...
var loader = serviceProvider.GetService<IDefinitionLoader>();
loader.LoadDefinition("<<json or yaml string here>>", Deserializers.Json);

Common DSL

Both the JSON and YAML formats follow a common DSL, where step types within the workflow are referenced by the fully qualified class names. Built-in step types typically live in the WorklfowCore.Primitives namespace.

Field	Description
Id	Workflow Definition ID
Version	Workflow Definition Version
DataType	Fully qualified assembly class name of the custom data object
Steps[].Id	Step ID (required unique key for each step)
Steps[].StepType	Fully qualified assembly class name of the step
Steps[].NextStepId	Step ID of the next step after this one completes
Steps[].Inputs	Optional Key/value pair of step inputs
Steps[].Outputs	Optional Key/value pair of step outputs
Steps[].CancelCondition	Optional cancel condition

json

{
  "Id": "HelloWorld",
  "Version": 1,
  "Steps": [
    {
      "Id": "Hello",
      "StepType": "MyApp.HelloWorld, MyApp",
      "NextStepId": "Bye"
    },        
    {
      "Id": "Bye",
      "StepType": "MyApp.GoodbyeWorld, MyApp"
    }
  ]
}

yaml

Id: HelloWorld
Version: 1
Steps:
- Id: Hello
  StepType: MyApp.HelloWorld, MyApp
  NextStepId: Bye
- Id: Bye
  StepType: MyApp.GoodbyeWorld, MyApp

Inputs and Outputs

Inputs and outputs can be bound to a step as a key/value pair object,

The Inputs collection, the key would match a property on the Step class and the value would be an expression with both the data and context parameters at your disposal.
The Outputs collection, the key would match a property on the Data class and the value would be an expression with both the step as a parameter at your disposal.

Full details of the capabilities of expression language can be found here

json

{
  "Id": "AddWorkflow",
  "Version": 1,
  "DataType": "MyApp.MyDataClass, MyApp",
  "Steps": [
    {
      "Id": "Hello",
      "StepType": "MyApp.HelloWorld, MyApp",
      "NextStepId": "Add"
    },
	{
      "Id": "Add",
      "StepType": "MyApp.AddNumbers, MyApp",
      "NextStepId": "Bye",
      "Inputs": { 
          "Value1": "data.Value1",
          "Value2": "data.Value2" 
       },
      "Outputs": { 
          "Answer": "step.Result" 
      }
    },    
    {
      "Id": "Bye",
      "StepType": "MyApp.GoodbyeWorld, MyApp"
    }
  ]
}

yaml

Id: AddWorkflow
Version: 1
DataType: MyApp.MyDataClass, MyApp
Steps:
- Id: Hello
  StepType: MyApp.HelloWorld, MyApp
  NextStepId: Add
- Id: Add
  StepType: MyApp.AddNumbers, MyApp
  NextStepId: Bye
  Inputs:
    Value1: data.Value1
    Value2: data.Value2
  Outputs:
    Answer: step.Result
- Id: Bye
  StepType: MyApp.GoodbyeWorld, MyApp

json

{
  "Id": "AddWorkflow",
  "Version": 1,
  "DataType": "MyApp.MyDataClass, MyApp",
  "Steps": [
    {
      "Id": "Hello",
      "StepType": "MyApp.HelloWorld, MyApp",
      "NextStepId": "Print"
    },
    {
      "Id": "Print",
      "StepType": "MyApp.PrintMessage, MyApp",
      "Inputs": { "Message": "\"Hi there!\"" }
    }
  ]
}

yaml

Id: AddWorkflow
Version: 1
DataType: MyApp.MyDataClass, MyApp
Steps:
- Id: Hello
  StepType: MyApp.HelloWorld, MyApp
  NextStepId: Print
- Id: Print
  StepType: MyApp.PrintMessage, MyApp
  Inputs:
    Message: '"Hi there!"'

You can also pass object graphs to step inputs as opposed to just scalar values

json

"inputs": 
{    
  "Body": {
      "Value1": 1,
      "Value2": 2
  },
  "Headers": {
      "Content-Type": "application/json"
  }
},

If you want to evaluate an expression for a given property of your object, simply prepend and @ and pass an expression string

json

"inputs": 
{    
  "Body": {
      "@Value1": "data.MyValue * 2",
      "Value2": 5
  },
  "Headers": {
      "Content-Type": "application/json"
  }
},

Enums

If your step has an enum property, you can just pass the string representation of the enum value and it will be automatically converted.

Environment variables available in input expressions

You can access environment variables from within input expressions. usage:

environment["VARIABLE_NAME"]