Tutorial by Examples: s

When to use Virtually all WPF controls make heavy use of dependency properties. A dependency property allows for the use of many WPF features that are not possible with standard CLR properties alone, including but not limited to support for styles, animations, data binding, value inheritance, and c...

When to use An attached property is a dependency property that can be applied to any DependencyObject to enhance the behavior of various controls or services that are aware of the property's existence. Some use cases for attached properties include: Having a parent element iterate through its c...

When to use A read-only dependency property is similar to a normal dependency property, but it is structured to not allow having its value set from outside the control. This works well if you have a property that is purely informational for consumers, e.g. IsMouseOver or IsKeyboardFocusWithin. How...

implode() combines all the array values but looses all the key info: $arr = ['a' => "AA", 'b' => "BB", 'c' => "CC"]; echo implode(" ", $arr); // AA BB CC Imploding keys can be done using array_keys() call: $arr = ['a' => "AA", 'b'...

These macros merge control flow and binding. They are an improvement over anaphoric anaphoric macros because they let the developer communicate meaning through naming. As such their use is recommended over their anaphoric counterparts. (if-let (user (get-user user-id)) (show-dashboard user) (...

JSON (JavaScript Object Notation) syntax is based on a subset of JavaScript (see also json.org). A valid JSON expression can be one of the following data types simple data types: String, Number, Boolean, Null composite data types: Value, Object, Array Simple data types A JSON string has to ...

A JSON Object is surrounded by curly braces and contains key-value pairs. { "key1": "value1", "key2": "value2", ... } Keys must be valid strings, thus surrounded by double quotation marks. Values can be JSON objects, numbers, strings, arrays, or one of the...

Html <img id="cats"></img> Dart import 'dart:html'; /// Stores the image in [blob] in the [ImageElement] of the given [selector]. void setImage(selector, blob) { FileReader reader = new FileReader(); reader.onLoad.listen((fe) { ImageElement image = document...

To prompt for credentials, you should almost always use the Get-Credential cmdlet: $credential = Get-Credential Pre-filled user name: $credential = Get-Credential -UserName 'myUser' Add a custom prompt message: $credential = Get-Credential -Message 'Please enter your company email address a...

The password in a credential object is an encrypted [SecureString]. The most straightforward way is to get a [NetworkCredential] which does not store the password encrypted: $credential = Get-Credential $plainPass = $credential.GetNetworkCredential().Password The helper method (.GetNetworkCrede...

To store and retrieve encrypted credentials easily, use PowerShell's built-in XML serialization (Clixml): $credential = Get-Credential $credential | Export-CliXml -Path 'C:\My\Path\cred.xml' To re-import: $credential = Import-CliXml -Path 'C:\My\Path\cred.xml' The important thing to remem...

Tuples are useful to swap values between 2 (or more) variables without using temporary variables. Example with 2 variables Given 2 variables var a = "Marty McFly" var b = "Emmett Brown" we can easily swap the values (a, b) = (b, a) Result: print(a) // "Emmett Bro...

The Common Lisp Quick Reference is a document which can be printed and bound as a booklet in various layouts to have a printed quick reference for Common Lisp.

You can remove all the elements in a set using the .clear() method: mySet.clear();

You can get the number of elements inside the set using the .size property const mySet = new Set([1, 2, 2, 3]); mySet.add(4); mySet.size; // 4 This property, unlike Array.prototype.length, is read-only, which means that you can't change it by assigning something to it: mySet.size = 5; mySet....

Unlike many other languages, Perl does not have constructors that allocate memory for your objects. Instead, one should write a class method that both create a data structure and populate it with data (you may know it as the Factory Method design pattern). package Point; use strict; sub new { ...

In general, classes in Perl are just packages. They can contain data and methods, as usual packages. package Point; use strict; my $CANVAS_SIZE = [1000, 1000]; sub new { ... } sub polar_coordinates { ... } 1; It is important to note that the variables declared in a packa...

To make a class a subclass of another class, use parent pragma: package Point; use strict; ... 1; package Point2D; use strict; use parent qw(Point); ... 1; package Point3D; use strict; use parent qw(Point); ... 1; Perl allows for multiple inheritance: package Point2D; use stri...

In Perl, the difference between class (static) and object (instance) methods is not so strong as in some other languages, but it still exists. The left operand of the arrow operator -> becomes the first argument of the method to be called. It may be either a string: # the first argument of new ...

To get the previous element you can use the .prev() method. <ul> <li>Mark</li> <li class="anna">Anna</li> <li>Paul</li> </ul> If you are standing on the "Anna" element and you want to get the previous element, &q...