generate pdf417 c# N-LEV EL UNDO in C#

Create PDF-417 2d barcode in C# N-LEV EL UNDO

CHAPTER 13 N-LEV EL UNDO
Draw PDF 417 In Visual C#.NET
Using Barcode generator for Visual Studio .NET Control to generate, create PDF417 image in .NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Reader In Visual C#.NET
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
The three operations are implemented by a set of three methods: CopyState() UndoChanges() AcceptChanges()
Drawing 2D Barcode In C#
Using Barcode maker for VS .NET Control to generate, create 2D Barcode image in .NET framework applications.
www.OnBarcode.com
Encoding EAN-13 In C#
Using Barcode printer for .NET framework Control to generate, create GTIN - 13 image in Visual Studio .NET applications.
www.OnBarcode.com
CopyState
Code 3/9 Encoder In Visual C#
Using Barcode printer for Visual Studio .NET Control to generate, create Code 39 Extended image in .NET framework applications.
www.OnBarcode.com
Painting Barcode In C#.NET
Using Barcode generator for .NET Control to generate, create Barcode image in .NET framework applications.
www.OnBarcode.com
The CopyState() method takes a snapshot of the object s current data and stores it in a Stack object.
Creating Universal Product Code Version A In C#
Using Barcode creator for .NET framework Control to generate, create Universal Product Code version A image in .NET applications.
www.OnBarcode.com
ISBN Maker In C#.NET
Using Barcode drawer for Visual Studio .NET Control to generate, create International Standard Book Number image in .NET applications.
www.OnBarcode.com
Stacking the Data
PDF417 Generation In None
Using Barcode generation for Office Word Control to generate, create PDF417 image in Microsoft Word applications.
www.OnBarcode.com
Recognizing PDF417 In VB.NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Since UndoableBase is an implementation of n-level undo capability, each object could end up storing a number of snapshots. As each undo or accept operation occurs, it gets rid of the most recently stored snapshot; this is the classic behavior of a stack data structure. Fortunately, the .NET Framework includes a prebuilt Stack<T> class that implements the required functionality. It is declared as follows: [NotUndoable] private Stack<byte[]> _stateStack = new Stack<byte[]>(); This field is marked as NotUndoable to prevent taking a snapshot of previous snapshots. CopyState() should just record the fields that contain actual business data. Once a snapshot has been taken of the object s data, the snapshot is serialized into a single byte stream. That byte stream is then put on the stack. From there, it can be retrieved and deserialized to perform an undo operation if needed.
GTIN - 12 Scanner In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Code-128 Maker In Objective-C
Using Barcode drawer for iPhone Control to generate, create Code 128C image in iPhone applications.
www.OnBarcode.com
Taking a Snapshot of the Data
Recognizing Barcode In .NET Framework
Using Barcode Control SDK for ASP.NET Control to generate, create, read, scan barcode image in ASP.NET applications.
www.OnBarcode.com
Paint Code 128B In Java
Using Barcode creator for Java Control to generate, create Code 128 Code Set C image in Java applications.
www.OnBarcode.com
The process of taking a snapshot of each field value in an object is a bit tricky. Reflection is used to walk through all the fields in the object. During this process, each field is checked to determine whether it has the NotUndoable attribute. If so, the field is ignored. The big issue is that field names may not be unique within an object. To see what I mean, consider the following two classes: namespace Test { public class BaseClass { int _id; } public class SubClass : BaseClass { int _id; } } Here, each class has its own field named _id, and in most circumstances it s not a problem. However, when using reflection to walk through all the fields in a SubClass object, it will return two _id fields: one for each of the classes in the inheritance hierarchy. To get an accurate snapshot of an object s data, CopyState() needs to accommodate this scenario. In practice, this means prefixing each field name with the full name of the class to which it belongs. Instead of two _id fields, the result is Test.BaseClass!_id and Test.SubClass!_id. The use of an exclamation point for a separator is arbitrary, but some character is necessary to separate the class name from the field name.
Decoding GTIN - 13 In VB.NET
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Code 128B Scanner In .NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
CHAPTER 13 N-LEV EL UNDO
Create ANSI/AIM Code 39 In Objective-C
Using Barcode encoder for iPhone Control to generate, create Code-39 image in iPhone applications.
www.OnBarcode.com
Code 128 Code Set C Recognizer In Visual Basic .NET
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
As if this weren t complex enough, reflection works differently with classes that are subclassed from other classes in the same assembly than with classes that are subclassed from classes in a different assembly. If in the previous example, BaseClass and SubClass are in the same assembly, one technique can be used; but if they re in different assemblies, a different technique is necessary. Of course, CopyState() should deal with both scenarios so the business developer doesn t have to worry about these details.
Encode Barcode In Java
Using Barcode creation for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
Generating Code 128B In .NET Framework
Using Barcode creation for .NET framework Control to generate, create Code-128 image in Visual Studio .NET applications.
www.OnBarcode.com
Note
Not all the code for UndoableBase is listed in this book. I only cover the key parts of the algorithm. For the rest of the code, refer to the download at www.apress.com/book/view/1430210192 or www.lhotka.net/cslanet/download.aspx.
The following method deals with all of the preceding issues. I walk through how it works after the listing: [EditorBrowsable(EditorBrowsableState.Never)] protected void CopyState() { CopyingState(); Type currentType = this.GetType(); HybridDictionary state = new HybridDictionary(); FieldInfo[] fields; if (this.EditLevel + 1 > parentEditLevel) throw new UndoException(string.Format( Resources.EditLevelMismatchException, "CopyState")); do { // get the list of fields in this type fields = currentType.GetFields( BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public); foreach (FieldInfo field in fields) { // make sure we process only our variables if (field.DeclaringType == currentType) { // see if this field is marked as not undoable if (!NotUndoableField(field)) { // the field is undoable, so it needs to be processed. object value = field.GetValue(this); if (typeof(Csla.Core.IUndoableObject). IsAssignableFrom(field.FieldType)) { // make sure the variable has a value
Copyright © OnBarcode.com . All rights reserved.