sitecore Workflow Set Item State and Executes actions in that state


Example

public void MoveToStateAndExecuteActions(Item item, ID workflowStateId)
{
    Sitecore.Workflows.IWorkflowProvider workflowProvider = Item.Database.WorkflowProvider;
    Sitecore.Workflows.IWorkflow workflow = workflowProvider.GetWorkflow(item);

    // if item is in any workflow
    if (workflow != null)
    {
        using (new Sitecore.Data.Items.EditContext(item))
        {
            // update item's state to the new one
            item[Sitecore.FieldIDs.WorkflowState] = workflowStateId.ToString();
        }

        Item stateItem = ItemManager.GetItem(workflowStateId, 
            Language.Current, Sitecore.Data.Version.Latest, item.Database, SecurityCheck.Disable);

        // if there are any actions for the new state
        if (!stateItem.HasChildren)
            return;

        WorkflowPipelineArgs workflowPipelineArgs = new WorkflowPipelineArgs(item, null, null);

        // start executing the actions
        Pipeline pipeline = Pipeline.Start(stateItem, workflowPipelineArgs);
        if (pipeline == null)
            return;
        WorkflowCounters.ActionsExecuted.IncrementBy(pipeline.Processors.Count);
    }
}

Thanks to this thread