crystal report barcode font free N-LEV EL UNDO in Visual Basic .NET

Generator QR in Visual Basic .NET N-LEV EL UNDO

CHAPTER 13 N-LEV EL UNDO
Generate QR-Code In Visual Basic .NET
Using Barcode creator for .NET Control to generate, create QR Code ISO/IEC18004 image in Visual Studio .NET applications.
www.OnBarcode.com
Quick Response Code Scanner In Visual Basic .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
formatter.Serialize(buffer, state) _stateStack.Push(buffer.ToArray()) End Using CopyStateComplete() End Sub <EditorBrowsable(EditorBrowsableState.Advanced)> _ Protected Overridable Sub CopyingState() End Sub <EditorBrowsable(EditorBrowsableState.Advanced)> _ Protected Overridable Sub CopyStateComplete() End Sub The CopyState() method is scoped as Protected because BusinessBase subclasses UndoableBase, and the BeginEdit() method in BusinessBase will need to call CopyState(). To take a snapshot of data, there needs to be somewhere to store the various field values before they are pushed onto the stack. A HybridDictionary is ideal for this purpose, because it stores name/ value pairs. It also provides high-speed access to values based on their names, which is important for the undo implementation. Finally, the HybridDictionary object supports .NET serialization, which means that it can be serialized and passed by value across the network as part of a business object. The CopyState() routine is essentially a big loop that starts with the outermost class in the object s inheritance hierarchy and walks back up through the chain of classes until it gets to UndoableBase. At that point, it can stop it knows that it has a snapshot of all the business data. At the start and end of the process, methods are called so a subclass can do pre- and postprocessing. Notice that CopyingState() and CopyStateComplete() are Overridable methods with no implementation. The idea is that a subclass can override these methods if additional actions should be taken before or after the object s state is copied. They provide an extensibility point for advanced business developers.
Data Matrix ECC200 Drawer In VB.NET
Using Barcode creator for Visual Studio .NET Control to generate, create DataMatrix image in .NET applications.
www.OnBarcode.com
Encode GS1 - 12 In VB.NET
Using Barcode creator for .NET Control to generate, create UCC - 12 image in .NET applications.
www.OnBarcode.com
Getting a List of Fields
Code39 Printer In Visual Basic .NET
Using Barcode generator for .NET framework Control to generate, create USS Code 39 image in VS .NET applications.
www.OnBarcode.com
Generate Barcode In Visual Basic .NET
Using Barcode generation for VS .NET Control to generate, create Barcode image in .NET framework applications.
www.OnBarcode.com
It s inside the loop where the real work occurs. The first step is to get a list of all the fields corresponding to the current class: ' get the list of fields in this type fields = currentType.GetFields(_ BindingFlags.NonPublic Or _ BindingFlags.Instance Or _ BindingFlags.Public) It doesn t matter whether the fields are Public they all need to be recorded regardless of scope. What s more important is to only record instance fields, not those declared as Shared. The result of this call is an array of FieldInfo objects, each of which corresponds to a field in the business object.
Making Code-128 In VB.NET
Using Barcode creation for Visual Studio .NET Control to generate, create Code 128 Code Set C image in Visual Studio .NET applications.
www.OnBarcode.com
Create EAN-8 In Visual Basic .NET
Using Barcode printer for VS .NET Control to generate, create EAN-8 Supplement 5 Add-On image in .NET framework applications.
www.OnBarcode.com
Avoiding Double-Processing of Fields
QR Code Generation In C#
Using Barcode maker for .NET framework Control to generate, create QR Code ISO/IEC18004 image in VS .NET applications.
www.OnBarcode.com
Reading QR Code ISO/IEC18004 In Visual C#.NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
As discussed earlier, the FieldInfo array could include fields from the base classes of the current class. Because of the way the JIT compiler optimizes code within the same assembly, if some base classes are in the same assembly as the actual business class, the same field name may be listed in multiple classes. As the code walks up the inheritance hierarchy, it could end up processing those fields twice. To avoid this, the code looks only at the fields that directly belong to the class currently being processed: For Each field As FieldInfo In fields ' make sure we process only our variables If field.DeclaringType = currentType Then
Draw EAN / UCC - 13 In None
Using Barcode printer for Font Control to generate, create EAN-13 Supplement 5 image in Font applications.
www.OnBarcode.com
Paint Barcode In Java
Using Barcode creator for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
CHAPTER 13 N-LEV EL UNDO
UCC - 12 Printer In .NET
Using Barcode creator for ASP.NET Control to generate, create UCC.EAN - 128 image in ASP.NET applications.
www.OnBarcode.com
DataMatrix Encoder In Objective-C
Using Barcode creation for iPhone Control to generate, create Data Matrix image in iPhone applications.
www.OnBarcode.com
Skipping NotUndoable Fields
Generating Barcode In Objective-C
Using Barcode creation for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
Read UPC A In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
At this point in the proceedings, it is established that the current FieldInfo object refers to a field within the object that s part of the current class in the inheritance hierarchy. However, a snapshot of the field should be taken only if it doesn t have the NotUndoable attribute: ' see if this field is marked as not undoable If Not NotUndoableField(field) Then Having reached this point, it is clear that the field value needs to be part of the snapshot, so there are two possibilities: this may be a regular field, or it may be a reference to a child object that implements Csla.Core.IUndoableObject.
Creating ECC200 In None
Using Barcode encoder for Online Control to generate, create ECC200 image in Online applications.
www.OnBarcode.com
USS Code 128 Scanner In Visual C#
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Cascading the Call to Child Objects or Collections
Drawing EAN / UCC - 13 In None
Using Barcode drawer for Software Control to generate, create GTIN - 13 image in Software applications.
www.OnBarcode.com
GS1-128 Generation In None
Using Barcode encoder for Office Word Control to generate, create UCC-128 image in Microsoft Word applications.
www.OnBarcode.com
If the field is a reference to a Csla.Core.IUndoableObject, the CopyState() call must be cascaded to that object so that it can take its own snapshot: If GetType(Csla.Core.IUndoableObject).IsAssignableFrom(field.FieldType) Then ' make sure the variable has a value If value Is Nothing Then ' variable has no value - store that fact state.Add(GetFieldName(field), Nothing) Else ' this is a child object, cascade the call DirectCast(value, Core.IUndoableObject).CopyState( _ Me.EditLevel + 1, BindingEdit) End If If a field has a Nothing value, a placeholder is put into the state dictionary so UndoChanges() can restore the value to Nothing if needed. Non-Nothing values represent a child object, so the call is cascaded to that child. Notice that the parent object doesn t directly manipulate the state of its children because that would break encapsulation. Instead, it is up to the child object to manage its own state. Keep in mind that if the child object is derived from BusinessListBase, the call will automatically be cascaded down to each individual child object in the collection.
Copyright © OnBarcode.com . All rights reserved.