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undoredo-ui.md

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uid title product categories summary
undoredo-ui
Adding Undo/Redo to the User Interface
postsharp
PostSharp;AOP;Metaprogramming
The document provides instructions on how to add Undo/Redo functionality to a user interface using PostSharp's ready-made WPF controls and custom controls. It also explains how to clear initial history.

Adding Undo/Redo to the User Interface

The Undo/Redo functionality that you added to your codebase needs to be made available to the users. Users will want to have the ability to move forward and backward through the stack of recorded operations.

Using the ready-made WPF controls

PostSharp includes two button controls xref:PostSharp.Patterns.Model.Controls.UndoButton and xref:PostSharp.Patterns.Model.Controls.RedoButton that you can add to your application.

To add Undo/Redo to a WPF window:

  1. Install the PostSharp.Patterns.Xaml package using NuGet.

  2. Add the following namespace declaration to the root element of your XAML file:

    xmlns:model="clr-namespace:PostSharp.Patterns.Model.Controls;assembly=PostSharp.Patterns.Xaml"

  3. To add Undo and Redo buttons to the user interface, including the following two lines of XAML.

    <model:UndoButton HorizontalAlignment="Left" Margin="22,24,0,0" VerticalAlignment="Top" />
<model:RedoButton HorizontalAlignment="Left" Margin="64,24,0,0" VerticalAlignment="Top"/>

    Your users are now able to make a changes in the user interface and Undo and/or Redo those changes at any point that they want.

Clearing the initial history

If we were to open the Customer management screen you would notice that the Undo button has a number of actions listed under it.

Those actions are listing the changes that were taken when the different Person instances were loaded and their properties were set. Most users will only want to see actions that they have manually taken in the screen. As such, you will need to manually interact with the xref:PostSharp.Patterns.Recording.Recorder to ensure that the Undo button list is empty when the window opens.

To provide an empty list of recorded actions when the window is initially opened, open the ViewModelMain class and find the constructor. Add the following as the last line in the constructor:

RecordingServices.DefaultRecorder.Clear();

The xref:PostSharp.Patterns.Recording.Recorder class is accessed through the xref:PostSharp.Patterns.Recording.RecordingServices.DefaultRecorder property. This property contains the current xref:PostSharp.Patterns.Recording.Recorder instance that is being used by the xref:PostSharp.Patterns.Recording.RecordableAttribute aspect. The xref:PostSharp.Patterns.Recording.Recorder class has two collections, xref:PostSharp.Patterns.Recording.Recorder.UndoOperations and xref:PostSharp.Patterns.Recording.Recorder.RedoOperations, which contain all of the past operations that can be undone and redone. The xref:PostSharp.Patterns.Recording.Recorder.Clear method removes all operations from both of those collections.

Now when you open the Customer management screen both the Undo and Redo buttons will show no history. This is the simplest type of Undo/Redo implementation that you can do. It will record each property change operation separately in the Undo and Redo UI buttons which probably isn’t what you, or your users, will want to see. Read xref:undoredo-operation-name to learn how to record groupings of operations that make sense to your business users.

Creating custom undo/redo controls

If the buttons provided by PostSharp don't meet your requirements, you can create your own controls for WPF, Windows Phone, WinRT, or any other platform.

Custom controls will typically provide a front-end to the global xref:PostSharp.Patterns.Recording.Recorder exposed by the xref:PostSharp.Patterns.Recording.RecordingServices.DefaultRecorder property. The controls could show the contents of the xref:PostSharp.Patterns.Recording.Recorder.UndoOperations and xref:PostSharp.Patterns.Recording.Recorder.RedoOperations collections. Controls typically use the xref:PostSharp.Patterns.Recording.Recorder.Undo and xref:PostSharp.Patterns.Recording.Recorder.Redo methods.