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Event Handling in Visual C ++

There are two images with two different images.

If I click on one block of the image, the image in it should be cleared.

To make matters worse, both picture boxes only have one common event handler. How can I find out which image is generating the event? I would appreciate the source code in C ++ - CLI

I need to know what to write inside the function:

private: System::Void sqaure_Click(System::Object^  sender, System::EventArgs^  e) {

}

EDIT: The problem is that when I try to send the sender to picurebox it gives an error saying the types cannot be converted.

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6 answers


How do you make the cast? In most cases, I would use:

PictureBox ^pb = safe_cast<PictureBox^>(sender);
if(pb != null) {
    // logic goes here
}

(Note that I fixed the above code after Josh pointed out my mistake. Thanks!)



a dynamic cast will give you the type of object you want if it can do, or null if it can't (that's the C # equivalent of "how")

If that gives you a null reference, then maybe your sender is not what you think?

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You can use the sender object. Transfer it to the image control unit and compare it with the two available boxes.



My Visual C ++ is a little rusty and can't provide the code now.

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kgiannakakis, The problem is when I try to send the sender to picurebox, it gives an error saying that the types cannot be converted.

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Are you sure the sender object is actually the type that you assume?

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If you are trying to use the code that Toji gave, then you cannot solve this problem:

PictureBox ^pb = safe_cast<PictureBox^>(sender);

Unlike C #, where you don't need the syntax to denote heap managed objects, C ++ \ CLI distinguishes between stack objects ( PictureBox pb

), heap object pointers ( PictureBox *pb

), and handles heap managed objects ( PictureBox ^pb

). These three are not the same thing, and have different lifetimes and uses.

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How are you trying to quit? I usually used dynamic_cast

either safe_cast

:

PictureBox ^ pb = dynamic_cast<PictureBox^>(sender);
if (pb != nullptr)
{
...
}

or

try
{
    PictureBox ^ pb = safe_cast<PictureBox^>(sender);
    ...
}
catch(InvalidCastException ^ exp)
{
    // Handle a cast that went awry
}

It should be pretty straight forward from there ...

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