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Hi, I want to hide the label forever,
Quite obvious, just hide it. That you have done yourself, too, right?
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even if the program is restarted
Now that is the problem. In this case you need to maintain the state of the program in a local file, a JSON file, XML, or something that you have defined for yourself.
The concept is serialization/deserialization, you would have to store the state of the application in the file and load it back again. Upon loading the file, you will then check whether to show the button or not.
I have written an article that speaks about the same concept in JSON, please read it and explore how you can use it to your own purpose,
From zero to hero in JSON with C#[
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