What exactly does the += mean in an eventhandler, how are the two different?

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Having a bit of trouble contemplating this rule here. What does the rule '+=' do in:

C#

private void button_Click(object sender, EventArgs e)
{
    Foo.Tick += Foo_Tick;
    Foo.Start();
}

void Foo_Tick(object sender, NewFrameEventArgs eventArgs)
{
    // Do sh*t...
}

thats different than just adding a timer to your form and starting it:

C#

private void button_Click(object sender, EventArgs e)
{
    timer1.Start();
}

private void timer1_Tick(object sender, EventArgs e)
{
    // Do sh*t...
}

What I have tried:

I want to be able to update a sequence of bitmap images to shows on screenm but I feel like a timer isn't enough to shows these images on time. Is a timer reliable enough to show motion at a high framerate from a sequence of images?

My code is not the issue, I just don't see what the difference is between the two functions.

Posted 1-Sep-21 15:30pm

Herboren

Updated 5-Sep-21 14:50pm

v3

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2 solutions

Solution 2

An Event is a special type of delegate (EventHandler) container; it is multi-cast, meaning that it maintains an "invocation list," an internal list of "subscribers" that it will "notify" any time it is executed (invoked).

I consider this is not equivalent to "assignment" of a value to a variable.

Think of the difference between;

"My phone number is #####"

and

"Please add my phone number, #####, to the list of people you call when Microsoft stock price drops more than US$ 20"

Posted 5-Sep-21 14:50pm

BillWoodruff

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OriginalGriff · Accepted Answer · 2021-09-01T19:57:00

It's not "+" and "=" as a "rule", it's the "+=" operator, which does a similaar thing to what it does for an integer:

C#

int x = 666;
x += 334;
Console.WriteLine(x);

Here it adds 334 to the existing value of 666 and prints the result: 1000
With an event handler, it does a similar thing: adds a handler to the event handler chain so that it gets called when the event is fired.

And no, a timer isn't "accurate" - it will happen "at some point" after the timeout period has elapsed, but your handler method isn't guaranteed to be called immediately the Tick happens. Windows isn't a real-time operating system which is the only time that timed events can be guaranteed to occur at a particular frequency.

I'd convert the images to a stream or video, and play that instead.