How to start share-point Workflow pragmatically using CSOM

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C#

SharePoint2010

SharePoint2013

Hello All,
I am trying to start share-point workflow using CSOM(Client side object model) by following means of code. But i got the following error from the line mark in comment. Please help me to figure out this error.

Error :- Cannot invoke method or retrieve property from null object. Object returned by the following call stack is null. "GetWorkflowDeploymentService
new Microsoft.SharePoint.WorkflowServices.WorkflowServicesManager()
"

 public bool StartWorkFlow()
 {
    private ClientContext _sharepoint = null;
    private Web _web = null;
    _sharepoint = new ClientContext("http://sharepoint/sites/dmdev/");
    _sharepoint.AuthenticationMode = ClientAuthenticationMode.Default;

    string workflowName = "UpdateDealStatus";

   // connect to the workflow services via a CSOM client context
   var workflowServicesManager = new WorkflowServicesManager(_sharepoint,                  _sharepoint.Web);

  // connect to the deployment service
   var workflowDeploymentService = workflowServicesManager.GetWorkflowDeploymentService();

  // get all installed workflows
  var publishedWorkflowDefinitions =    workflowDeploymentService.EnumerateDefinitions(true);
            _sharepoint.Load(publishedWorkflowDefinitions);

   try
   {
      _sharepoint.ExecuteQuery();//Error thrown from this line
   }
   catch (Exception ex)
   {
                
                
   }

   // find the first workflow definition
   var firstWorkflowDefinition = publishedWorkflowDefinitions.First();

   // connect to the subscription service
   var workflowSubscriptionService = workflowServicesManager.GetWorkflowSubscriptionService();

   // get all workflow associations
   var workflowAssociations = workflowSubscriptionService.EnumerateSubscriptionsByDefinition(firstWorkflowDefinition.Id);
   
   _sharepoint.Load(workflowAssociations);
   _sharepoint.ExecuteQuery();

   foreach (var association in workflowAssociations)
   {
       Console.WriteLine("{0} - {1}",
       association.Id, association.Name);
   }
    return true;
}