How to trigger a sharepoint custom list workflow programmatically

I have a custom list and associated workflow with it. It is working fine from within SharePoint, but the workflow is not triggered when new item is added from a WebPart.

I have added SPWorkflowAssociation which is also not helping.

SPSecurity.RunWithElevatedPrivileges(delegate()
{
  using (SPSite site = new SPSite(SPContext.Current.Site.Url))
  {
    site.AllowUnsafeUpdates = true;
    using (SPWeb web = site.OpenWeb())
    {
     web.AllowUnsafeUpdates = true;
     SPList ListEmployeeNew = web.Lists["CustomList"];
     SPWorkflowAssociationCollection asscoll = ListEmployeeNew.WorkflowAssociations;
     SPListItem newItem = ListEmployeeNew.AddItem();
     newItem["First Name"] = "Fist Name";
     newItem["Last Name"] = "Last Name";
     newItem.Update();
     foreach (SPWorkflowAssociation spwfa in asscoll)
     {
       site.WorkflowManager.StartWorkflow(newItem, spwfa, spwfa.AssociationData);
     }
     web.AllowUnsafeUpdates = false;
   }
 }
});