了解Revit扩展存储数据（Extensible Storage）

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原文链接： http://blog.csdn.net/joexiongjin/article/details/7776552
作者：  叶雄进 , Autodesk ADN

从Revit2012开始引入了扩展存储这个新技术，就是可以把一些数据存储到Revit中的某一个对象上。扩展数据只能通过编程的方式添加到对象上，通过Revit软件的界面无法添加。这是编程的一个大优势。你可以把任何的数据保存在Revit中的任何一个对象上。你自己的扩展数据始终跟着这个Rvt文件走，不会丢失。 而且存储的数据可以设置访问权限。对于保密数据可以只能是你自己的程序读取，或只有具有特殊的开发者代号的程序才能访问。对于数据的保密性非常有帮助。

创建共享参数步骤：

创建并命名新的数据架构（Schema）
设置数据架构（Schema）读写访问权限
向数据架构增加字段（一个或多个）
基于数据架构创建一个数据对象（Entity）
给数据对象Entity中的字段赋值
关联数据对象Entity和Revit模型中的对象

下面时段代码演示：

    public Result Execute(      ExternalCommandData commandData,      ref string message,      ElementSet elements)    {      UIDocument uiDoc = commandData.Application.ActiveUIDocument;      Document doc = uiDoc.Document;      // Create transaction for working with schema      Transaction trans = new Transaction(doc, "Extensible Storage");      trans.Start();      // Select a wall element      Wall wall = null;      try      {        Reference r = uiDoc.Selection.PickObject(ObjectType.Element,          new WallSelectionFilter());        wall = doc.GetElement(r) as Wall;      }      catch (Autodesk.Revit.Exceptions.OperationCanceledException)      {        message = "Nothing selected; please select a wall to attach extensible data to.";        return Result.Failed;      }      Debug.Assert(null != wall, "expected a wall to be selected");      if (null == wall)      {        message = "Please select a wall to attach extensible data to.";        return Result.Failed;      }      // Create a schema builder      SchemaBuilder builder = new SchemaBuilder(_guid);      // Set read and write access levels      builder.SetReadAccessLevel(AccessLevel.Public);      builder.SetWriteAccessLevel(AccessLevel.Public);      // Note: if this was set as vendor or application access,       // we would have been additionally required to use SetVendorId      // Set name to this schema builder      builder.SetSchemaName("WallSocketLocation");      builder.SetDocumentation("Data store for socket related info in a wall");      // Create field1      FieldBuilder fieldBuilder1 =        builder.AddSimpleField("SocketLocation", typeof(XYZ));      // Set unit type      fieldBuilder1.SetUnitType(UnitType.UT_Length);      // Add documentation (optional)      // Create field2      FieldBuilder fieldBuilder2 =        builder.AddSimpleField("SocketNumber", typeof(string));      //fieldBuilder2.SetUnitType(UnitType.UT_Custom);      // Register the schema object      Schema schema = builder.Finish();      // Create an entity (object) for this schema (class)      Entity ent = new Entity(schema);      Field socketLocation = schema.GetField("SocketLocation");      ent.Set<XYZ>(socketLocation, new XYZ(2, 0, 0), DisplayUnitType.DUT_METERS);      Field socketNumber = schema.GetField("SocketNumber");      ent.Set<string>(socketNumber, "200");      wall.SetEntity(ent);      // Now create another entity (object) for this schema (class)      Entity ent2 = new Entity(schema);      Field socketNumber1 = schema.GetField("SocketNumber");      ent2.Set<String>(socketNumber1, "400");      wall.SetEntity(ent2);      // Note: this will replace the previous entity on the wall       // List all schemas in the document      string s = string.Empty;      IList<Schema> schemas = Schema.ListSchemas();      foreach (Schema sch in schemas)      {        s += "\r\nSchema Name: " + sch.SchemaName;      }      TaskDialog.Show("Schema details", s);      // List all Fields for our schema      s = string.Empty;      Schema ourSchema = Schema.Lookup(_guid);      IList<Field> fields = ourSchema.ListFields();      foreach (Field fld in fields)      {        s += "\r\nField Name: " + fld.FieldName;      }      TaskDialog.Show("Field details", s);      // Extract the value for the field we created      Entity wallSchemaEnt = wall.GetEntity(Schema.Lookup(_guid));      XYZ wallSocketPos = wallSchemaEnt.Get<XYZ>(        Schema.Lookup(_guid).GetField("SocketLocation"),        DisplayUnitType.DUT_METERS);      s = "SocketLocation: " + Format.PointString(wallSocketPos);      string wallSocketNumber = wallSchemaEnt.Get<String>(        Schema.Lookup(_guid).GetField("SocketNumber"));      s += "\r\nSocketNumber: " + wallSocketNumber;      TaskDialog.Show("Field values", s);      trans.Commit();      return Result.Succeeded;    }