csomStart2010ListWorkflow.cs

using Microsoft.SharePoint.Client;
using Microsoft.SharePoint.Client.Workflow;
using Microsoft.SharePoint.Client.WorkflowServices;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security;

namespace CSOMWorkflow
{
    class Program
    {
        static void Main(string[] args)
        {
            //Replace the following values according to your configuration.

            //Site Details
            string siteUrl = "https://mytenant.sharepoint.com/sites/test";
            string userName = "user@mytenant.onmicrosoft.com";
            string password = "password";

            //Name of the SharePoint2010 List Workflow
            string workflowName = "SP2010DocWF";

            //Name of the List to which the Workflow is Associated
            string targetListName = "Documents";
            
            //Guid of the List to which the Workflow is Associated
            Guid targetListGUID = new Guid("b89e266c-5f20-4b83-9f95-10a42c629e84");
            
            //Guid of the ListItem on which to start the Workflow
            Guid targetItemGUID = new Guid("6ab8227b-66a3-4e12-8055-846dcfb53cab");

            using (ClientContext clientContext = new ClientContext(siteUrl))
            {
                SecureString securePassword = new SecureString();

                foreach (char c in password.ToCharArray()) securePassword.AppendChar(c);

                clientContext.Credentials = new SharePointOnlineCredentials(userName, securePassword);

                Web web = clientContext.Web;

                //Workflow Services Manager which will handle all the workflow interaction.
                WorkflowServicesManager wfServicesManager = new WorkflowServicesManager(clientContext, web);

                //Will return all Workflow Associations which are running on the SharePoint 2010 Engine
                WorkflowAssociationCollection wfAssociations = web.Lists.GetByTitle(targetListName).WorkflowAssociations;

                //Get the required Workflow Association
                WorkflowAssociation wfAssociation = wfAssociations.GetByName(workflowName);

                clientContext.Load(wfAssociation);

                clientContext.ExecuteQuery();

                //Get the instance of the Interop Service which will be used to create an instance of the Workflow
                InteropService workflowInteropService = wfServicesManager.GetWorkflowInteropService();

                var initiationData = new Dictionary<string, object>();

                //Start the Workflow
                ClientResult<Guid> resultGuid = workflowInteropService.StartWorkflow(wfAssociation.Name, new Guid(), targetListGUID , targetItemGUID, initiationData);

                clientContext.ExecuteQuery(); 
            }
        }
    }
}