Introduction to Delegates and Events This lesson introduces delegates and events. Our objectives are as follows: These reference types allowed you to create instances of objects and use them in special ways to accomplish your software development goals. Classes allow you to create objects that contained members with attributes or behavior. Interfaces allow you to declare a set of attributes and behavior that all objects implementing them would publicly expose. A delegate is a C language element that allows you to reference a method. The answer boils down to giving you maximum flexibility to implement any functionality you want at runtime. Think about how you use methods right now. You write an algorithm that does its thing by manipulating the values of variables and calling methods directly by name. What if you wanted an algorithm that was very flexible, reusable, and allowed you to implement different functionality as the need arises?
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Net managing Active Directory objects is a bit lengthy and you need a good knowledge on the principal store to have your head around on what you want to do. We ususally use the System. DirectoryServices namespace but with.
C# implements delegates and events as first-class language elements. In contrast, the Java delegation event model is essentially a bolted-on technology, providing a complex and bloated solution to an original event model that never worked well in the first place.
July 29, Shasta dam under construction source: Wikimedia Commons This is an excerpt from C 6. The book offers more than code recipes to common and not-so-common problems that C programmers face every day. Problem You want to be able to build up an object to work with on the fly at runtime. Solution Use ExpandoObject to create an object that you can add properties, methods, and events to and be able to data bind to in a user interface. We can use ExpandoObject to create an initial object to hold the Name and current Country of a person.
One example of why you might do this is to add properties to your object from another source of data. We will add the Language property. In our example, we will add a validation method for our object: We will add two events, LanguageChanged and CountryChanged. CountryChanged looks at the Country that changed and invokes the LanguageChanged event with the proper Language for the Country.
Lesson Anonymous Methods
Occurs when the interval elapses. TimersDescription “Occurs when the Interval has elapsed. ElapsedEventHandler Elapsed; member this. Elapsed event every two seconds milliseconds , sets up an event handler for the event, and starts the timer.
Remember to keep the HookProc delegate alive manually, such as using a class member as shown in the example below, otherwise the garbage collector will clean up your hook delegate eventually, resulting in your code throwing a ferenceException.
We can query an application’s state to find out the current state of the world, and this answers many questions. However there are times when we don’t just want to see where we are, we also want to know how we got there. Event Sourcing ensures that all changes to application state are stored as a sequence of events.
Not just can we query these events, we can also use the event log to reconstruct past states, and as a foundation to automatically adjust the state to cope with retroactive changes. How it Works The fundamental idea of Event Sourcing is that of ensuring every change to the state of an application is captured in an event object, and that these event objects are themselves stored in the sequence they were applied for the same lifetime as the application state itself.
Let’s consider a simple example to do with shipping notifications. In this example we have many ships on the high seas, and we need to know where they are. A simple way to do this is to have a tracking application with methods to allow us to tell when a ship arrives or leaves at a port.
Why C# Is Not Java
Events One of the things that the language designers considered when designing the C language was the ability to notify external callers of certain events happening. To solve this problem, they surprise surprise introduced the event construct. One of the oddities in the design however, comes in the form of virtual events. This is one of those design decisions that we recognize is something we would like to change, but as my colleague, Eric Lippert explains in a series of posts concerning breaking changes , we aren’t able to fix everything that we would like to.
How virtual events work So first off, lets quickly describe how virtual events work. A virtual event declaration specifies that the accessors of that event are virtual.
How to consume ETW events from C#. Tuesday, February 3, Now I want to show you how to collect ETW events using C#. hook the event “EventArrived” in your code and then just set the property Enabled to true to start the asynchronous processing of the ETW Events.
NET developers have to deal with: This can be a pretty heated debate; people love to defend the tools they love. Once you get down to work, though, both languages are very similar. They both have access to the same libraries and tools, they both have full support from Microsoft and enormous developer communities, and they both get the job done well. But there are differences.
Sure, both languages have code generation and IntelliSense and code snippets, and yes, you can come up with examples where VB code is shorter and more elegant than C.
Events: Demystifying Common Memory Leaks
Expand I would like to draw your attention to an interesting aspect of C language design. Thus, Hejlsberg probably could not resist the temptation to keep C open ended by providing a trap door to access the runtime, without having to add additional syntax. Attributes have been put to varied use ranging from calling DLL JDirect legacy to switching between managed and unmanaged codes, and even to modify the synchronization semantics.
To highlight this point, I will use the Threading Synchronization design and implementation of C.
The prepare-commit-msg hook is run before the commit message editor is fired up but after the default message is created. It lets you edit the default message before the commit author sees it. This hook takes a few parameters: the path to the file that holds the commit message so far, the type of commit, and the commit SHA-1 if this is an amended commit.
However, I was looking for a quick way without going through those process to deploy demo site for this blog on a VPS. For this simple purpose, git hook seemed a legit idea. Thus I went for this adventure of simple automated deployment with git hook. There are several articles showing the process in various steps. Also, I did fell into several obstacle in the way, with several confusions as not being a professional in area of server administration.
However, finally, I did able to set this up which seems to be working well. Here is what I was trying to do: Set up private Git server on a Ubuntu Using single Git repository instead of multiple for both development and production server. Implement the push to deploy mechanism using git post-receive hook. So, final outcome will be that, I will be able to do my development on local machine and after push to the git server, it will update the web application automatically without any need to ssh to server etc.
Lets drive into the details. Set up private Git server on ubuntu: The official documentation about git on ubuntu is pretty much enough to follow.
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December 31, 3 Comments In plain old. In WPF the idea is still the same, but updated to take into account the rather complex visual trees that often occur in WPF. In WPF, when an event is raised on an element in the visual tree, the event will either travel up the visual tree from the element till it reaches the root or down the tree from the root to the element.
BulletChrome Grid caught preview event from Microsoft. BulletChrome Button caught preview event from Microsoft.
C# book for beginners, that walk you through design, building, publishing – start to finish examples? up to date and simple Low Level Keyboard and Mouse Hook library for a bigger project that I’m working on but I couldn’t find any. (All that I found was an outdated library that was made using Visual Studio ) so, I made my own.
We would love for you to install the prototype and try it out on your code! Or maybe a copy of it! Read on for an in-depth discussion of the design and rationale, and scroll to the end for instructions on how to get started! The billion-dollar mistake Tony Hoare , one of the absolute giants of computer science and recipient of the Turing Award, invented the null reference! I call it my billion-dollar mistake. It was the invention of the null reference in
The following procedures show how to hook up an existing method to an event by getting all the necessary types through reflection, and how to create a dynamic method using reflection emit and hook it up to an event. Note For another way to hook up an event-handling delegate, see the code example for the AddEventHandler method of the EventInfo class. To hook up a delegate using reflection Load an assembly that contains a type that raises events.
Assemblies are usually loaded with the Assembly.
Mike Woodring’ Sample Page. This page contains sample code I’ve written to demonstrate various things on platform. If you have specific questions about any of these samples, you can email me at [email protected] If you have general questions that aren’t specifically about the code in my samples, please do not email me.
Click the banner to return to the series jump page! Each of the items covered in this post came from requests from my readers. Handling UI Events This is the part that has me the most excited, mostly because I just learned about how to do it, and it solves so many issues. Want to have your GUI run a chunk of code when the user edits a textBox. Or handle the event which is triggered if the user moves the mouse over a button? We can even wait till the user is finished entering text, and then run a short chunk of code to validate an entry.
These are all real world scenarios for a User Interface Developer, and we can easily deal with them in PowerShell. I like to draw a somewhat wide tab, like this. Then, right-click the top of the tab…uh, holder, right next to your last tab and choose Layout-Fill All. This will expand the tabs to fill the whole UI.