WPF XAML demo: Difference between revisions

Please read the Dyalog tutorials for a more detailed explanation. Part of the code was taken from ''[http://www.codeproject.com/Articles/22980/WPF-A-Beginner-s-Guide-Part-of-n CodeProject: A Beginner's Guide]''.

=== What is XAML? ===

[[wikipedia:XAML|XAML]] stands for Extensible Application Markup Language (and pronounced "Zammel"). It's a simple language based on [[wikipedia:XML]] to create and initialize [[.NET]] objects with hierarchical relations.

You can use WPF without using XAML. It's up to you whether you want to declare it in XAML or write it as code.  There is a [https://msdn.microsoft.com/en-us/library/ms752059(v=vs.100).aspx XAML Overview] from Microsoft.

{{Collapse|Here is an example of XAML found in the attached namespace called '''sample1''':|

<source lang=apl inline>FixSimpleXaml</source> is a function used to execute the XAML and return the root element as a .Net object.  All the other elements that are named in the XAML will be attached to their names to the root object automatically.

That way you don't need to define a separate variable for each named element. If you install the [[user command]] called <source lang=apl inline>sfPropGrid</source> you can see all the properties, methods and events of all the named objects by doing (click the combo of NOE to access all the named objects):

In conclusion <source lang=apl inline>FixSimpleXaml</source> is a simple function to use on simple XAML that does not have events and is properly formed.  In production code you may want to do something like this:

     ⍝ Fixing the XAML did not work. Show an error and exit.

     ⎕ ← 'Error Fixing XAML'

{{Collapse|For cases where there are events that need to be fixed and have better error handling the function <source lang=apl inline>FixXaml</source> is available.  It is useful when using XAML taken directly from Visual Studio.  For example, with the XAML code in '''sample2''' that has an event on the button (Click<nowiki>=</nowiki>"<source lang=apl inline>__Button_Click</source>") at line 24, if you do the following:|

The goal is to be able to take the XAML directly from Visual Studio to APL.  The single underscore '_' is a valid first character in Visual Studio and APL but is in conflict with the menu object that will accept an underscore as the first character to define a keyboard shortcut.

     ⍝ Fixing the XAML did not work. Show an error and exit.

In general, when using XAML there is no need to define a <source lang=apl inline>⎕USING</source> before fixing it except when there is a 3rd party dll involved.  For example, the variable <source lang=apl inline>NewWindow</source> is defined as:

The first element of XAML must contain the '''xmlns=''' and the '''xmlns:x=''' declarations. This is instructing the parser (in our case '''System.Windows.Markup.!XamlReader''' in the function <source lang=apl inline>FixSimpleXaml</source> and <source lang=apl inline>FixXaml</source>) to load a series of .NET namespaces required to parse the XAML.  This is just a convention, there is actually no such web site.

When using 3rd party dll, they must be added to the declaration in the first element of XAML.  There are 2 choices on how to do it:

and the XAML will look like this:

but this is not enough, <source lang=apl inline>⎕USING</source> must be set up correctly before fixing the XAML for 3rd party dlls in order for the parser to find the assembly.  Here is an example for the Syncfusion !PropertyGrid ('''Syncfusion/4.5/''' is the Dyalog sub-directory where the assemblies live):

In XAML you declare an Image object that is on disk the following way:

When you want to keep the Image definition in the APL workspace (because it is easier that way to distribute the workspace or the namespace) one way of doing it is by keeping a [[wikipedia:Base64|Base64]] definition of the Image. Base64 encoding is using a set of 64 visible characters to encode binary data.

It is widely used on the internet, for example in emails for images and binary attachments.

At design time, save the images in the workspace.  The APL variable name of any image must be the original name of the image name in the XAML with the added suffix '''_b64''' (naming convention only).

If there are many images in the XAML, the following lines of code can automate the process at run time:

{{Collapse|The function <source lang=apl inline>ScrubAndFix</source> will remove all the events from the XAML by looping on a <source lang=apl inline>XamlXmlReader</source> object. It is slower than <source lang=apl inline>FixXaml</source> but the events don't need to have a specific prefix.  Perfect for experimenting with the XAML taken directly from the Web.  All the named objects are attached to the root object|

     ⍝ Function to remove the Class and Events elements of XAML and fix the resulting XAML.

     ⍝ This function is most usefull when experimenting with XAML taken directly from the Web but is slower than FixXaml.

           ⎕USING,←'System.IO' 'System.Windows.Markup,WPF/PresentationFramework.dll' 'System.XAML,System.XAML.dll'

The User Command [[wpfXamlEditor||]] is designed to edit the XAML saved in the workspace and on disk.

You can insert a WPF control into an already existing application developed with <source lang=apl inline>⎕WC</source> by using an [https://msdn.microsoft.com/en-us/library/system.windows.forms.integration.elementhost(v=vs.110).aspx ElementHost] and a Dyalog's <source lang=apl inline>NetControl</source>. Here is an example of how to insert a WPF Button:

If you have a repetitive task to be executed on the UI thread then you can use a [https://msdn.microsoft.com/en-us/library/system.windows.threading.dispatchertimer(v=vs.110).aspx DispatcherTimer] like this:

The .NET framework provides a simple way to get started in threading with the [https://msdn.microsoft.com/fr-fr/library/cc221403(v=vs.95).aspx BackgroundWorker] component. This wraps much of the complexity and makes spawning a background thread relatively safe. It offers several features which include spawning a background thread, the ability to cancel the background process before it has completed, and the chance to report the progress back to your UI. The <source lang=apl inline>BackgroundWorker</source> is an excellent tool when you want multithreading in your application with access to the UI thread, mainly because it's so easy to use.

An example is included in this namespace. It is inspired by [http://www.wpf-tutorial.com/misc/multi-threading-with-the-backgroundworker/ this article].  You start the example by doing:

# Download [[attachment:wpfXamlDemo.v1.6.txt]]

# Do a Select all (Ctrl+A) and a copy (Ctrl+C).

# In your workspace execute <source lang=apl inline>)ed ⍟ wpfXamlDemo </source>

# Paste (Ctrl+V) the text into the Dyalog editor

# Press Escape and ')save' your workspace