Could anyone please explain what and how this code below is doing/working?
RoleEnvironment.Chaning += RoleEnvironmentChaning;
private void RoleEnvironmentChanaing(object sender, RoleEnvironmentchaningnEventArgs e)
{
......
}
basically, if you could walk me through how event handling works in c#.net will be greatly appreciated.
Thanks.
Let's forget about C# for a second and think about the following scenario.
You have a button on the screen that you want the user to click, you don't know when the user will click the button and neither do you want to check constantly if the user has clicked the button. What you want to do is run a bit of custom code when the user does eventually click on a button.
Welcome to events or delegates.
Let's take a look at the button.
The Button has a Click event that you can hook your custom code onto.
i.e.
//This happens in the designer
Button button = new Button();
button.Click += new EventHandler(YourMethod);
Your method will now be called once the button has been clicked.
What happens on Click of the button? Someone will check whether or not there are subscribers to the event
if(Click != null)
{
Click(this, someEventArguments);
}
Basically that's saying: whenever the RoleEnviroment decided to trigger the "changing" event, call that method. (I assume it should be Changing rather than Chaning or Chanaing as per your code.)
In other words, events in C# are an implementation of the publisher/subscriber or observer pattern.
See my article on events and delegates for more information.
Some first page search results:
http://www.codeproject.com/KB/cs/csevents01.aspx
http://www.c-sharpcorner.com/UploadFile/ddutta/EventHandlingInNetUsingCS11092005052726AM/EventHandlingInNetUsingCS.aspx
http://msdn.microsoft.com/en-us/library/aa645739%28VS.71%29.aspx
Related
I has rey use VS 2015 with xamarin forms to create a cross platform project. I add the xaml page which contain a text box and button. In the code behind, I has code as below
public Inno()
{
InitializeComponent();
btntest.Clicked += Btntest_Clicked;
}
Private void Btntest_Clicked(object sender, EventArgs e)
{
if(string.IsNullOrEmpty(Name.Text))
{
return;
}
}
When I run the android simulator to test the page, it fire the constructor. But when I clicke the button, it not fire the click event. Anything goes wrong? Please help. Thanks
Theres a few things you can try:
hook up the event handler in the xaml, see if that works - because you are subscribing to the event in the constructor this shouldn't make a difference functionality wise.
Edit: to do this, in your xaml:
<Button Clicked="buttonClicked" />
and Press tab when intellisense prompts you to create a new handler.
as #hankide said - set a breakpoint and make sure it isn't actually entering it and that the problem isn't the code inside the event handler.
You need to make sure that your btntest object has been properly mapped to the button on the XAML side of things. By default, XAML objects don't have "names" as you may be accustomed to in WinForms or WebForms and need to have a name property assigned to them. For me, I typically have my buttons marked up as:
<Button x:Name=btntest Text="Click Me></Button>
Then in the code behind I have to find the button by name in order to wire up the event:
var testButton = this.FindByName<Button>("btntest");
testButton.Clicked += Btntest_Clicked;
From there everything works as expected.
Try this:
btntest.Clicked += new EventHandler(Btntest_Clicked);
Thanks everyone for the answer...not sure why I close the solution and re-open it, it work fine.
So, I would double click here on my designer
and it should create me the code, but well it doesn't. And there is no value changed event in the events either.
So if anyone knows how to fix this, it would be nice. (I doubt it) so how would I get around this? How would I go on about creating the code myself that should be created when I double click on it?
Click the form or control that you want to create an event handler for.
In the Properties window(F4), click the Events button
In the list of available events, click the event that you want to create an event handler for.
In the box to the right of the event name, type the name of the handler and press ENTER.
Add the appropriate code to the event handler.
To create an event handler in the code editor
Switch to the code editor by using one of the following techniques:
Create a new method like:
private void buttonName_Click(object sender, EventArgs e) { ... }
In the file YourFormName.Designer.cs find your button and add
this.buttonName.Click += new System.EventHandler(this.buttonName_Click);
What I'm trying to do is get my winform to display a debug line when ever I click in my winform. However, when I do, nothing happens. I know how to get a button / other click event to happen. But what I need is to be able to click anywhere within my winform.
I've googled this for the past hour but can't see what I'm doing wrong. As far as I'm aware, this code should be correct in detecting a mouse click. This method is held withing the form1.cs class:
private void mouseClick(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
Trace.WriteLine("Mouse clicked");
}
I've tried setting brake points, but these don't get triggered either. What is it I'm doing wrong?
Sorry for the stupidly newbie question, but I am very new to winform programming.
How to add the EventHandler:
public Form1()
{
InitializeComponent();
// This line should you place in the InitializeComponent() method.
this.MouseClick += mouseClick;
}
Using the editor built-in to Visual Studio:
Go to the properties window (if you don't see it, press Alt + Enter).
Select the events icon (looks like lightning).
Double-click on the empty ComboBox to the right of Click.
You'll be taken to an empty method where you can put your code.
The method itself is correct. I think your actual problem is: you haven't added this method to MouseClick events.
In C# – and most other languages too – event is handled by an event handler. Windows forms and controls have events for all the events happening in your controls, such as OnClick or OnResize.
You can append methods to these events, and the methods will automatically get called when the actual event happens. Simply add the following line to your form's constructor, Form_Load-method, InitializeComponent-method, or such:
this.MouseClick += mouseClick;
Now when ever MouseClick event happens, your method mouseClick will be called automatically.
I would recommend reading Events C# Programming Guide. You need to add an event handler like so:
form1.MouseClick += mouseClick;
I have written a custom control in C# (inherited from Forms.Control) and it seems to working fine, but if you press the button fast enough a problem occurs: only every other click will call the click event handler. This doesn't happen if you don't press it fast (less than once a second). The mouseUp and mouseDown handlers always get called no matter how fast you click the button.
Of course doesn't happen with the canned winform button.
I cannot use the canned button because I'm writing an application for the .net compact framework, so I need a custom control in order to make the UI more presentable. Also, I tested out my code on the full version of the .net framework, and I still have the same problem.
Any help would be greatly appreciated. Thank you!
If you are clicking rapidly enough, you are getting into DoubleClick territory.
According to above MSDN Page the order of events are:
The following series of events is raised by the control when such a user action takes place:
MouseDown event.
Click event.
MouseClick event.
MouseUp event.
MouseDown event.
DoubleClick event.
MouseDoubleClick event.
MouseUp event
If you will notice there is only one Click event per DoubleClick
For a way to disable it try looking at this MSDN Page discussing ControlStyles.
From above link:
StandardClick -- If true, the control implements the standard Click behavior.
StandardDoubleClick -- If true, the control implements the standard DoubleClick behavior. This style is ignored if the StandardClick bit is not set to true.
So try this in your controls constructor or load event:
this.SetStyle(ControlStyles.StandardClick, true );
this.SetStyle(ControlStyles.StandardDoubleClick, false);
Since SetStyle does not appear to be in the Compact Framework you could add a DoublClick Event and have it trigger the Click event Programmically like this.
YourClickEvent(sender, new MouseEventArgs(System.Windows.Forms.MouseButtons.Left,1,0,0,0));
When you click your control fast enough, it calls double click rather than click.
So, you should do something like this in your click function:
{
control.Enabled = false;
......
control.Enabled = true;
}
I was wonder how can I fire an event when the user double click on my webbrowser component. Since it has no such event how it could be possible...
Thanks in advance
Sounds like a WPF matter :-)
There you would go with an Behaviour attached to the browser. See this link for more information about this approach if you can alter your application (dependends on what you have done yet).
If you can't apply this solution, just bind a event handler to the click event and count click per time with respect to the mouse movement since the last click and if both conditions are true (two clicks in 0.2 secs, mouse hasn't moved more than 2px, for example) execute your double click code. The events you should use are previewMOUSEdown or MOUSEdown, not KEYdown.
// Call this where you want to create the event (let's say on the form load for example).
webBrowser1.DoubleClick += new EventHandler(webBrowser1_DoubleClick);
// This happens when the event is fired (so when you double click on the webbrowser control).
void webBrowser1_DoubleClick(object sender, EventArgs e)
{
// Code
}
Try this.
I don't know why you can't set this event via the designer :(, but this should work.