Microsoft Windows Workflow Foundation

using System;
using System.Collections.Generic;
using System.Text;
using System.Workflow.Runtime;
using System.Workflow.Runtime.Hosting;

namespace MVDataChecker
{
    public static class WorkflowFactory
    {
        // Singleton instance of the workflow runtime
        private static WorkflowRuntime _workflowRuntime = null;

        // Lock (sync) object
        private static object _syncRoot = new object();

        // Factory method
        public static WorkflowRuntime GetWorkflowRuntime()
        {
            // Lock execution thread in case of multi-threaded
            // (concurrent) access.
            lock (_syncRoot)
            {
                // Check for startup condition
                if (null == _workflowRuntime)
                {
                    // Provide for shutdown
                    AppDomain.CurrentDomain.ProcessExit += new EventHandler(StopWorkflowRuntime);
                    AppDomain.CurrentDomain.DomainUnload += new EventHandler(StopWorkflowRuntime);

                    // Not started, so create instance
                    _workflowRuntime = new WorkflowRuntime();

                    // Start the runtime
                    _workflowRuntime.StartRuntime();
                } // if

                // Return singleton instance
                return _workflowRuntime;
            } // lock
        }

        // Shutdown method
        static void StopWorkflowRuntime(object sender, EventArgs e)
        {
            if (_workflowRuntime != null)
            {
                if (_workflowRuntime.IsStarted)
                {
                    try
                    {
                        // Stop the runtime
                        _workflowRuntime.StopRuntime();
                    }
                    catch (ObjectDisposedException)
                    {
                        // Already disposed of, so ignore...
                    } // catch
                } // if
            } // if
        }
    }
}