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How to change button click event into enter event?

I'm new on C#, I made a button which makes appear another button and I want to remove the click event of this new one and change it into an enter(key) event.
Code1
Code2
When the button appears it only works when I click it but no when I press Enter.

As to your question, https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.control.enter?view=net-5.0
The enter event is for when keyboard or mouse enter the control (button in this case).
From the sounds of your question, you are wanting to click the button when the 'Enter' key is pressed.
If this is WinForms, then you might actually want a property on the parent form called 'AcceptButton' (https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.form.acceptbutton?view=net-5.0). This will make it so anytime the Enter key is hit (with the exception of controls such as a RichTextBox that accepts the return key) that button will be clicked (course you still need the button click event for the button).
Although you seem to be doing something weird in your example code image, so I'm not sure that's the correct solution for it. Instead, you need to look at maybe the Keyboard events, such as KeyPress (https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.control.keypress?view=net-5.0). There are several: KeyDown, KeyPress, KeyUp, and PreviewKeyDown.
Note these events require Keyboard focus on the control in question. So if add them to the button you are creating in your example code, then that button will need keyboard focus to receive the keyboard events.
Also, just FYI, if a button has keyboard focus, by default the SpaceBar will click that button for you, while the Enter key is generally reserved for clicking the Form's AcceptButton.

cannot set cancel button to forms?

I'm learning on programming with C# windows forms. Then I discover cancelButton property. I try to set this property to my form so that when I hit ESC it would close my form. But when I double click cancelButton in my form's property, there nothing happen except VS marks my Form1.cs as unsaved. No method created after the double click. I tried to create private void cancelButon(object sender, EventArgs e){} but the dropdown box where I select method for cancelButton refuses to show my method. The same thing happens to AcceptButton. I have tried to create a brand new project, but it would not help.
Is that VS's bug, or am I missing something?

You've misunderstood what the form's CancelButton and AcceptButton properties are for...
To make the form's CancelButton property work you first have to add a button to the form. Then you select that button from the drop-down list next to the form's CancelButton property.
What this does is to automatically click the Cancel button when the user presses the Escape key.
Similar logic applies to the form's AcceptButton property, except that it will cause the associated button to be clicked when the user presses the Enter key.
Having done that, you STILL HAVE TO ADD A HANDLER FOR THE BUTTON CLICKS.
To do that, double-click on the button in the form (displayed in the designer) - that is what will automatically add the handler for you.
To summarise:
Form.CancelButton -> Determines which button will be clicked when user presses Escape.
Form.AcceptButton -> Determines which button will be clicked when user
presses Enter.
To add a handler for a button, double click the button in the designer.

Omit action when pressing Enter on button

Is there a way to omit the (whatever) performed action on a button when the key is pressed? I already got some good inputs from SO and tried to catch the event via OnKeyPress or OnKeyDown - but I could not omit the Enter-action. I also liked the idea of disabling the Tabstop property, but as soon as I click the button the problem reoccurs.
OnKeyDown only seems to fire when "casual" keys (like a or z) are pressed, but not when Enter is hit. How can I detect it - when Enter is hit - on the button itself?

When you press ENTER inside a non-multiline field on a form with a default button set, the click event for this button is fired, like a click, not like a keyevent (keypress, keyup, keydown, etc).
Form.AcceptButton
Gets or sets the button on the form that is clicked when the user
presses the ENTER key.
If you don't want this behaviour (or want to prevent it), maybe you should remove it as the default button.
But if you need it to be default only in certain situations, you can bind/unbind it programatically:
form1.AcceptButton = btnSave;
form1.AcceptButton = null;

You can use : if(e.KeyCode == Keys.Enter){}

Check the Button.IsDefault property

Well, the fact that
When you press ENTER [...] the click event for this button is fired
made me think about the use of the OnMouseUp(MouseEventArgs e) method instead of OnClick(EventArgs e). I gave it a shot and it totally fits my requirements - plus: it gives me the opportunity to only exclude the wrapped buttons from said issue, not involving any other controls in my application (like Form.AcceptButton).
Thanks for all your input, which made me think about the issue from another perspective!

Control's Focused property has changed as of Leave handler when using mouse, but not keyboard

I am working with a TextBox, and need to fire some logic when the textbox has lost focus.
My problem is twofold:
The Leave event is firing on every keypress for some reason, meaning the logic is run with every keypress when it should not.
When using the Focused property of the Textbox as a double-check, simply exiting out if the property is still set, it now works when the user uses the mouse to leave, but not when the user tabs out.
The Focused property of the TextBox in question is False as of when its Leave event fires when the mouse is used to change focus, but it is still True when the Leave event fires due to a Tab keypress. Seriously?
I need a workaround, because the logic firing on every keystroke is causing a problem for users right now that needs to be fixed post-haste.

I created a form with a textbox on it and attached event handler to the leave event of that text box. I then typed a bunch of stuff into said textbox. The event was not raised. I hit tab, the event was raised. I then clicked back in the textbox, typed some more, and then clicked another control and the event was raised.
I'm just saying that something else is interfering with the textbox. I would look into that a little more, or post some code demonstrating the problem.

Stop textbox leave handler on click of exit button?

I have a form where I do some validations in a textbox and a button for closing the form. Now whenever I click the button and focus is on text box, the leave handler is called.
How can I stop textbox leave handler from executing ?
update :
The text of button in E&XIT, now whenever I press Atl + X it calls the button click event, but when I click on the button it doesn't. Why is it happening ?
Thanks.

Use the Validating event instead of the Leave event. Set the button's CausesValidation property to False.