As you might have heard many times, the Workflow Architecture in SharePoint 2013 was entirely changed from what it was in SharePoint 2010. Instead of the Workflows running on the SharePoint server, they now have to run on a separate Workflow Manager.
On top of that, only declarative custom Workflow's are allowed to be deployed to the Workflow Manager. If there has to be any custom code, it has to be hosted in an external service and then consumed from the declarative workflow.
The Workflow Manager has certain activities and types which come predefined with it. This is called the Trusted Surface. Workflow Authors can consume these activities in their declarative workflows. A whole list of types and activities available under the trusted surface is here: http://msdn.microsoft.com/en-us/library/jj193509(v=azure.10).aspx and here: http://msdn.microsoft.com/en-us/library/jj193474(v=azure.10).aspx
This architecture is very much inline with Microsoft's strategy to move code execution away from the SharePoint server.
On top of that, only declarative custom Workflow's are allowed to be deployed to the Workflow Manager. If there has to be any custom code, it has to be hosted in an external service and then consumed from the declarative workflow.
The Workflow Manager has certain activities and types which come predefined with it. This is called the Trusted Surface. Workflow Authors can consume these activities in their declarative workflows. A whole list of types and activities available under the trusted surface is here: http://msdn.microsoft.com/en-us/library/jj193509(v=azure.10).aspx and here: http://msdn.microsoft.com/en-us/library/jj193474(v=azure.10).aspx
This architecture is very much inline with Microsoft's strategy to move code execution away from the SharePoint server.
SharePoint 2013 supports two methods of workflow authoring. Authoring Workflows in the SharePoint 2013 engine and also authoring them in the SharePoint 2010 engine. Workflows which are authored in the SharePoint 2010 engine run on the SharePoint server and are allowed to execute code there. That architecture has not been changed and is available for backwards compatibility.
In the SharePoint 2013 Workflow platform, a Workflow definition is a Service Bus Topic and a Workflow Association is a Subscription to the topic. Topics and Subscriptions are used by the Service Bus to decouple message publishers from message subscribers. More about the Workflow Manager and Service Bus Pub/Sub architecture here: http://msdn.microsoft.com/en-us/library/office/jj163181(v=office.15).aspx#bkm_Subscriptions
In the SharePoint 2013 Workflow platform, a Workflow definition is a Service Bus Topic and a Workflow Association is a Subscription to the topic. Topics and Subscriptions are used by the Service Bus to decouple message publishers from message subscribers. More about the Workflow Manager and Service Bus Pub/Sub architecture here: http://msdn.microsoft.com/en-us/library/office/jj163181(v=office.15).aspx#bkm_Subscriptions
Microsoft has also very recently added Workflow Management services to the Client Side Object Model (CSOM). The entire range of Workflow services available in the CSOM is published here: http://msdn.microsoft.com/en-us/library/office/dn481315(v=office.15).aspx. In this post, and the following posts, I will show you how to manage workflows with CSOM.
This is code works with SharePoint 2013 On-Premises as well as with SharePoint Online. I have created my sample code against SharePoint Online. Also, this code only works with Workflows which are authored on the SharePoint 2013 Workflow Engine. I will be writing another post on the CSOM Interop Service in which I will show how to start SharePoint 2010 Workflow Engine authored Workflows.
Before you run this code, you will need to create a Workflow (Definition) either via SharePoint Designer 2013 or through Visual Studio 2012/2013 and deploy it to your target site. You can then use this code to dynamically create associations of the Workflow, and also to start those associations.
You will need to reference the following Assemblies:
Microsoft.SharePoint.Client.dll
Microsoft.SharePoint.Client.Runtime.dll
Microsoft.SharePoint.Client.WorkflowServices.dll