WF4.0自定义持久化

    WF4提供了强大的持久化的功能，ms提供了SqlWorkflowInstanceStore 来进行SqlServer的持久化，我研究了一下，DB里面有10个数据表，24个存储过程。功能非常强大，但是也逻辑也比较复杂。这里我介绍自定义的持久化。持久化的存储器也SqlServer。

1、设计数据表，表结构非常简单，如下图所示：

  

2、自定义的SqlServerWorkflowInstanceStore继承了InstanceStore：

 public class SqlServerWorkflowInstanceStore : InstanceStore
    {
      public  Guid ownerInstanceID;
        
        public SqlServerWorkflowInstanceStore() : this(Guid.NewGuid())
        {

        }

        public SqlServerWorkflowInstanceStore(Guid id)
        {
            ownerInstanceID = id;
        }

        //Synchronous version of the Begin/EndTryCommand functions
        protected override bool TryCommand(InstancePersistenceContext context, InstancePersistenceCommand command, TimeSpan timeout)
        {
            return EndTryCommand(BeginTryCommand(context, command, timeout, null, null));
        }

        //The persistence engine will send a variety of commands to the configured InstanceStore,
        //such as CreateWorkflowOwnerCommand, SaveWorkflowCommand, and LoadWorkflowCommand.
        //This method is where we will handle those commands
        protected override IAsyncResult BeginTryCommand(InstancePersistenceContext context, InstancePersistenceCommand command, TimeSpan timeout, AsyncCallback callback, object state)
        {
            IDictionary<System.Xml.Linq.XName, InstanceValue> data = null;

            //The CreateWorkflowOwner command instructs the instance store to create a new instance owner bound to the instanace handle
            if (command is CreateWorkflowOwnerCommand)
            {
                context.BindInstanceOwner(ownerInstanceID, Guid.NewGuid());
            }
            //The SaveWorkflow command instructs the instance store to modify the instance bound to the instance handle or an instance key
            else if (command is SaveWorkflowCommand)
            {
                SaveWorkflowCommand saveCommand = (SaveWorkflowCommand)command;
                data = saveCommand.InstanceData;
                Save(data);
            }
            else if (command is LoadWorkflowCommand)
            {

                try
                {
                        InstancesTable obj = InstancesTableBiz.GetInstancesTable(this.ownerInstanceID);
                        System.Text.UTF8Encoding utf8 = new System.Text.UTF8Encoding();
                        byte[] bs = utf8.GetBytes(obj.InstanceXML);
                        System.IO.MemoryStream memoryStream = new System.IO.MemoryStream(bs);
                        data = LoadInstanceDataFromFile(memoryStream);
                        context.LoadedInstance(InstanceState.Initialized, data, null, null, null);
                }
                catch (Exception exception)
                {
                    throw new PersistenceException(exception.Message);
                }
            }

            return new CompletedAsyncResult<bool>(true, callback, state);
        }

        protected override bool EndTryCommand(IAsyncResult result)
        {
            return CompletedAsyncResult<bool>.End(result);
        }

        IDictionary<System.Xml.Linq.XName, InstanceValue> LoadInstanceDataFromFile(Stream inputStream)
        {
            IDictionary<System.Xml.Linq.XName, InstanceValue> data = new Dictionary<System.Xml.Linq.XName, InstanceValue>();

            NetDataContractSerializer s = new NetDataContractSerializer();

            XmlReader rdr = XmlReader.Create(inputStream);
            XmlDocument doc = new XmlDocument();
            doc.Load(rdr);

            XmlNodeList instances = doc.GetElementsByTagName("InstanceValue");
            foreach (XmlElement instanceElement in instances)
            {
                XmlElement keyElement = (XmlElement)instanceElement.SelectSingleNode("descendant::key");
                System.Xml.Linq.XName key = (System.Xml.Linq.XName)DeserializeObject(s, keyElement);

                XmlElement valueElement = (XmlElement)instanceElement.SelectSingleNode("descendant::value");
                object value = DeserializeObject(s, valueElement);
                InstanceValue instVal = new InstanceValue(value);

                data.Add(key, instVal);
            }

            return data;
        }

        object DeserializeObject(NetDataContractSerializer serializer, XmlElement element)
        {
            object deserializedObject = null;

            MemoryStream stm = new MemoryStream();
            XmlDictionaryWriter wtr = XmlDictionaryWriter.CreateTextWriter(stm);
            element.WriteContentTo(wtr);
            wtr.Flush();
            stm.Position = 0;

            deserializedObject = serializer.Deserialize(stm);

            return deserializedObject;
        }

        void Save(IDictionary<System.Xml.Linq.XName, InstanceValue> instanceData)
        {
            XmlDocument doc = new XmlDocument();
            doc.LoadXml("<InstanceValues/>");
            
            foreach (KeyValuePair<System.Xml.Linq.XName,InstanceValue> valPair in instanceData)
            {
                XmlElement newInstance = doc.CreateElement("InstanceValue");

                XmlElement newKey = SerializeObject("key", valPair.Key, doc);
                newInstance.AppendChild(newKey);

                XmlElement newValue = SerializeObject("value", valPair.Value.Value, doc);
                newInstance.AppendChild(newValue);

                doc.DocumentElement.AppendChild(newInstance);
            }
            if (!string.IsNullOrEmpty(InstancesTableBiz.GetInstancesTable(this.ownerInstanceID).InstanceXML))
            {
                InstancesTable obj = InstancesTableBiz.GetInstancesTable(this.ownerInstanceID);
                obj.InstanceXML = doc.InnerXml;
                InstancesTableBiz.UpdateInstancesTable(obj);
            }
            else
            {
                InstancesTable obj = new InstancesTable();
                obj.id = this.ownerInstanceID;
                obj.InstanceXML = doc.InnerXml;
                InstancesTableBiz.AddInstancesTable(obj);
            }
   
       }

        XmlElement SerializeObject(string elementName, object o, XmlDocument doc)
        {
            NetDataContractSerializer s = new NetDataContractSerializer();
            XmlElement newElement = doc.CreateElement(elementName);
            MemoryStream stm = new MemoryStream();
            s.Serialize(stm, o);
            stm.Position = 0;
            StreamReader rdr = new StreamReader(stm);
            newElement.InnerXml = rdr.ReadToEnd();
            return newElement;
        }  
    }

3、设计书签类：

    public sealed class Read<TResult> : NativeActivity<TResult>
    {
        public Read()
            : base()
        {
        }

        public string BookmarkName { get; set; }

        // Must return true for a NativeActivity that creates a bookmark
        protected override bool CanInduceIdle
        { 
            get { return true; } 
        } 

        protected override void Execute(NativeActivityContext context)
        {
            context.CreateBookmark(this.BookmarkName, new BookmarkCallback(this.Continue));
        }

        void Continue(NativeActivityContext context, Bookmark bookmark, object obj)
        {
            this.Result.Set(context, (TResult)obj); 
        }
    }

 4、设计三个书签的流程：

5、自定义持久化的使用

  SqlServerWorkflowInstanceStore  instanceStore = new  SqlServerWorkflowInstanceStore ();

            WorkflowApplication application = new WorkflowApplication(new Activity1());

            application.InstanceStore = instanceStore;

            application.PersistableIdle = (e) =>
            {
                return PersistableIdleAction.Unload;
            };
            application.Completed = (workflowApplicationCompletedEventArgs) =>
            {
                Console.WriteLine("\nWorkflowApplication has Completed in the {0} state.", workflowApplicationCompletedEventArgs.CompletionState);
            };

            application.Unloaded = (workflowApplicationEventArgs) =>
            {
                Console.WriteLine("WorkflowApplication has Unloaded\n");
                instanceUnloaded.Set();
            };

            instanceStore.ownerInstanceID = application.Id;
        
            // continue executing this instance
            application.Run();

           //string a= application.GetBookmarks()[0].BookmarkName;

            instanceUnloaded.WaitOne();

            return application.Id; ;

6、Demo说明：

    在Start.aspx，启动一个流程

    在Default.aspx，进行A,B,C三个站的审核。

备注：运行环境是VS2010 BETA2。

代码：/Files/zhuqil/WorkflowConsoleApplication3.rar

（全文完）

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