Persisting of Workflow in the file

This post contains one very simple working example of the WorkflowPersistenceService which persist workflow instances in the file store.

using System;

using System.Collections.Generic;

using System.Text;

using System.Workflow.Runtime.Hosting;

using System.Workflow.ComponentModel;

using System.IO;

using System.Workflow.Runtime;

using System.Diagnostics;

namespace Daenet.Workflow

{

    /// <summary>

    /// Implements the custom WorkflowPersistenceService, which persists workflow instances in the file.

    /// </summary>

    public class WFFilePersistenceProvider : WorkflowPersistenceService

    {

        /// <summary>

        ///

        /// </summary>

        /// <param name="folder">The folder where the instance will be persisted.</param>

        public WFFilePersistenceProvider(string folder)

        {

            m_Folder = folder;

            if (Directory.Exists(folder) == false)

                Directory.CreateDirectory(folder);

        }

        private string m_Folder = "WFPersistance";

        #region Serialization

        /// <summary>

        /// Performs the serialization of one activity. Invoked during dehydration.

        /// </summary>

        /// <param name="RootActivity"></param>

        /// <param name="id"></param>

        private void SerializeActivity(Activity RootActivity, Guid id)

        { 

            string filename = getFileName(ref id);

            lock (typeof(WFFilePersistenceProvider))

            {

                using (FileStream stream = new FileStream(filename, FileMode.OpenOrCreate))

                {

                    RootActivity.Save(stream);

                }

            }

        }

        /// <summary>

        /// Performs deserialization of persisted activity. Invoked during rehydration.

        /// </summary>

        /// <param name="RootActivity"></param>

        /// <param name="id"></param>

        /// <returns></returns>

        private object DeserializeActivity(Activity RootActivity, Guid id)

        {

            string filename = getFileName(ref id);

            lock (typeof(WFFilePersistenceProvider))

            {

                using (FileStream stream = new FileStream(filename, FileMode.Open))

                {

                    object Result = Activity.Load(stream, RootActivity);

                    return Result;

                }

            }

        }

        #endregion

        #region Private Members

        private string getFileName(ref Guid id)

        {

            string filename = m_Folder + "\\" + id.ToString() + ".wf";

            return filename;

        }

        private Guid getIdFromFileName(string fileName)

        {

            int pos = fileName.LastIndexOf("\\");

            if (pos == -1)

                throw new ApplicationException("Serialization in the root is not
                supported. Please specify the folder which will contain persisted files.");

            string guidStr = fileName.Substring(pos + 1, fileName.Length - 4 - pos);

            return new Guid(guidStr);

        }

        #endregion

        #region Provider Members

        #region WorkflowProvider Interface Implementation

        protected override System.Workflow.ComponentModel.Activity

            LoadCompletedContextActivity(Guid scopeId,
            System.Workflow.ComponentModel.Activity outerActivity)

        {

            Trace.WriteLine("Rehydration");

            object obj = DeserializeActivity(outerActivity, scopeId);

            return (Activity)obj;           

        }

        protected override System.Workflow.ComponentModel.Activity LoadWorkflowInstanceState(Guid instanceId)

        {

            Trace.WriteLine("Rehydration");

            object obj = DeserializeActivity(null, instanceId);

            return (Activity)obj;

        }

        protected override void SaveCompletedContextActivity(System.Workflow.ComponentModel.Activity activity)

        {

            Guid contextGuid = (Guid)activity.GetValue(Activity.ActivityContextGuidProperty);

            SerializeActivity(activity, contextGuid);

        }

        protected override void SaveWorkflowInstanceState
        (System.Workflow.ComponentModel.Activity rootActivity, bool unlock)

        {

            // Remove this "if" statement, if you want to persist workflow in any status.

            if (rootActivity.ExecutionStatus == ActivityExecutionStatus.Executing)

            {

                Guid contextGuid = (Guid)rootActivity.GetValue(Activity.ActivityContextGuidProperty);

                SerializeActivity(rootActivity, contextGuid);

            }

        }

        protected override bool UnloadOnIdle(System.Workflow.ComponentModel.Activity activity)

        {

            return false;

        }

        protected override void UnlockWorkflowInstanceState(System.Workflow.ComponentModel.Activity rootActivity)

        {

        }

        #endregion

        public void PersistWorkflow(WorkflowInstance wInstance)

        {

            Activity rootActivity = wInstance.GetWorkflowDefinition();

            SaveWorkflowInstanceState(rootActivity, true);

        }

        /// <summary>

        /// This method traverses all serializaed wirkflow instances and loads Loads
        /// persisted workflows.

        /// </summary>

        /// <returns></returns>

        public ICollection<WorkflowInstance> LoadPersistedWorkflows()

        {

            List<WorkflowInstance> persistedWorkflows = new List<WorkflowInstance>();

            string[] files = Directory.GetFiles(m_Folder, "*.wf");

            foreach (string file in files)

            {

                Guid id = getIdFromFileName(file);

                persistedWorkflows.Add(this.Runtime.GetWorkflow(id));

            }

            return persistedWorkflows;

        }

        /// <summary>

        /// Deletes all existing serialized files. After this call no workflow remains in the store.

        /// </summary>

        public void Clean()

        {

            string[] files = Directory.GetFiles(m_Folder, "*.wf");

            foreach (string file in files)

            {

                File.Delete(file);

            }

        }

        #endregion

    }

}

This code snippet shows how to programmatically add the custom workflow persistence service:

WFFilePersistenceProvider persistanceService = new WFFilePersistenceProvider("c:\\temp\\WFPersistance");

WorkflowRuntime runtime = new WorkflowRuntime();

runtime.AddService(persistanceService);