Correlation Tokens in SharePoint workflow

Correlation tokens are unique identifiers in SharePoint that bridges to map the objects between the workflow and windows workflow environment. Windows workflow acts as a intermediate layer to communicate with other software. When incoming request arrives, runtime receives the request and determines the request and identifies the workflow instance. Then it process the request for the instance.

Windows workflow acts as a communication channel for all the workflow instances. We can have two separate correlation tokens for Workflows and task references. We cannot assign the correlation token to workflow task that used for workflow.

We have to declare the correlation token for the workflow in OnWorkflowActivated activity. We have to bind the this correlation token to  each activity in the workflow.

OnWorkflowActivated activity raises when workflow initiated  for SharePoint. This is the first event raised in workflow. Each task should have its own correlation token that provides the task related information. 

SharePoint 2013 - Workflows

Workflow, One of the Major Change from SharePoint 2010 to Share Point 2013. In SharePoint 2010 workflows developed and will run on Workflow foundation 3.5. Microsoft people choose a new path in share point 2013.  workflows will run on windows workflow foundation 4.5. In 2013 workflow is not hosted by share point  Now all new share point 2013 workflows are hosted by a new product, windows azure workflow. This is separate from share point 2013. Below are imaged showing Workflow changes in SharePoint 2010 to SharePoint 2013.

SharePoint still supporting .net framework 3,5 workflows. But this only to execute share point 2010 workflows. In Windows Azure Workflows also we have facility to call .net 3.5 workflows using Interop activity.

When creating new workflow and publishing workflow to share point 2013, SharePoint retains the value and publishes Windows Azure Workflow server. When we call the workflow in share point  it will ask Windows Azure Workflow server to start the workflow and pass the context to the workflow. Windows Azure Workflow uses Client Object Model for information and run the workflow.

As SharePoint 2010, There is some built in options for retry the workflows. We'll have this feature in SP2013 and Windows Azure Workflows. This feature will keep on trying to call the alternative if any problem with the workflow. Things will queued up for later on process. There is lot of API's in Client Object Model, to view and interact with the workflow. We also use some REST API's in windows Azure Workflows to check what' happening.

create workflows

Big change from 2010 workflows to 2013 workflow frameworks, there is no custom code. All the workflows are declarative it was created by Designer or visual studio 2012. We can create a WCF service and host it as out side of SharePoint and access it using HTTP  actions. Here the advantage is we can call service either designer or visual studio.

Some big improvements in SharePoint 2013 designer is that we have loops in share point 2013, and we can use office controls like, COPY/PASTE etc..

Stages in Workflows

Here Replacement of share point State machine workflows, a new concept called Stages. A workflow can have one or more stages. Each stage will have Gate and end. It determines where to start and where to go next or end depends on the condition.

What's new in SharePoint designer Workflows 

As mentioned earlier we have Loops and office controls , also we have visual designer through visio. So that we can have the ability to edit the workflow properties.

Workflows through Visual Studio

The new change in vs 2013, we can create workflows declaratively  we can use custom code create WCF service and host it out of share point  We can use HTTP activities to activities and call WCF services. There is new Data type called Dynamic Value. So that we can get the data returned by WCF.

What is "Dynamic Value Data Type"

When we call WCF service through HTTP, it will return an object type "Dynamic Value". This is new data type in Windows Azure Workflow. We can use other activity to pull data from Dynamic Value. using XPATH notation.

Workflows with Apps

Yes, We can create workflow as app in share point. Using workflow as logic to Apps. So here code must be Client side code. Suppose, in a case that we need to send email to users, an workflow will be created in app. When app deployed to site, it will call Workflow located in Windows Azure Servers, and workflow will call WCF service having custom code.