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perform a hotkey when press a graphical button

I got a thought experiment with a graphical user interface for writing a command.
There are buttons for saving, writing cursive and so on.....
Now when i press the button save, i want to that the compiler perform Ctrl+S like in every textdocument, or change the marked one to cursive with Ctrl+Shift+K.
I tried to set the variable to the value of the ascii code, but this ain´t worked. Now i need help that the compiler perform the hotkey.
Is there a function in C# or is there another way to realize that.

Actually those hotkeys are implemented functions of the programs you use (e.g. word). The hotkey just executes the same function as the button you can press - the compiler doesn't know the hotkey Ctrl+Shift+K.
Just think about it: If the compiler knew about those hotkeys, it would have to know how to make the selected text in the focused textbox cursive - wouldn't this be kind of strange?
I might misunderstand your question, maybe you just wanted to ask how to type text with a simulated keyboard for the form, because you already implemented the shortcut functionability. In that case you'd have two options:
Call the function called when you press the specified shortcut
Actually simulate keypresses to the form
The second one is done like that:
SendKeys.Send("^S"); //For Ctrl+S - ^ is the Control button
For other special keys with the SendKeys function take a look at this: https://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.aspx.

Button with no hWnd

Good evening folks,
I'm building a simple application (A) that sends Strings to a textbox of another application (B). I was able to this step, but afterwards I'd like to automatically press a button placed just under the textbox. The problem is that I can't get the Handle of the Button; using "Window Detective"(similiar to Spy++), I see only the textboxes (called "TEdit", see the attachments) and no Buttons!. I'd like to add also that there's no only a Button but 3!! So, how could I press a specific Button? Is there another chance to get the Handle?
Program "target"
Window Detective screenshot

Based on the class name TEdit that's a VCL application probably coded in Delphi. The buttons are likely TSpeedButton and non-windowed. You won't be able to send them messages and they are not automatable.
Faced with this your best hope of success is to fake input. Fake the mouse click at the appropriate location on the form. It's not pretty but there's little option.

Sending text into whatever window that is currently in focus

I'm trying to write a program with C# that sends text into other windows.
How do I write a command in C# that sends a text into the window that is currently under the users focus?
For example:
If the user clicks an open notepad window, or an open outlook letter, or an open excel sheet, and then clicks the button on my program, a text will be "pasted" directly into the last notepad window/outlook letter/excel cell that the user clicked on last.
I hope my question is clear enough. I'm not so experienced and am missing a lot of terminology.

Take your application out of focus by minimizing or hiding the main window, and then send your text with
SendKeys.SendWait("Hello World!");
Finally, restore your main window.
If the code is executed in the main form, you could do this
this.Visible = false;
SendKeys.SendWait("Hello World!");
this.Visible = true;

Olivier's response actually seems more accurate (and taught me something :)) than my original "does not seem achievable". If you need an example, then take a look at this:
http://www.codeproject.com/Articles/18366/Sending-Keystrokes-to-another-Application-in-C
However, on a more complex level, without an API to call into, there is not much more that you can do beyond this solution.

C# WinForms Wait on form to proceed

I'm tired and hungry, so I might of missed it, but from what I can see no existing post covers this...
I'm writing a plugin for an application. My plugin loads a form to get some data specifically, it uses the webcam to scan for a barcode. Once it's found a barcode, the form hides itself (incase it's needed again later). This is how I currently call the form that does the barcode work:
string readData = null;
if (eye == null)
{
System.Windows.Forms.Application.EnableVisualStyles();
eye = new CamView();
}
eye.Show();
if (eye.found)
{
readData = eye.readData;
}
return readData;
So, my problem is that eye.show() doesn't block. It makes the form appear and carries right on before there's a chance for the barcode to appear. I imagine I need to use some form of threading or locking, but my crude attempts to do so have just frozen the interface completely.
The "eye" form is basically just a viewfinder for the webcam, and relies on the camera_OnImageCapture event to make it do it's image checks for the barcode.
Is there an elegant way to make the application calling the plugin wait for the form to finish? Or do I just need to add an accept button to the "eye form?"
Cheers. And humble apologies if this is in anyway a repost.

.ShowDialog();
http://msdn.microsoft.com/en-us/library/c7ykbedk.aspx
"You can use this method to display a modal dialog box in your application. When this method is called, the code following it is not executed until after the dialog box is closed."

You are on the right track. You change the code to show CamView as a modal dialog but do no add an Accept button. Instead change camera_OnImageCapture to close the dialog.

How do I read MessageBox text using WinAPI

How do I read a message of standard Win message box (Info)?
Using
SendMessage(this.HandleControl, WM_GETTEXT, builder.Capacity, builder);
I can only read the header of the message box or the text of the button, but not the message itself.
thanks.
Notes (from Q&A):
this.HandleControl is a handler to the message box window
Spy++ shows no child controls bar the button. That's what it made me thinking that Message Boxes have their own way of keeping text w/out using labels
It's a legacy app written with delphi, the button's class is TButton as per Spy++, but still there's no controls except of button inside the dialog window.
After checking a notepad window, both Image & Text are 'selectable', I guess my app doesn't use a std MessageBox. still, how do I go about extracting the text out of the thing? I can see that no labels in my delphi app can be selected by Spy++ Finder tool.

The message text is in a label control on the modal MessageBox dialog window. You have to get the window handle to the MessageBox dialog (win32 API FindWindow) then retrieve the window handle to the control (win32 API GetDlgItem) and then retrieve the text from that window win32 API GetWindowText).
EDIT --
TCHAR text[51] = {0};
HWND msgBox = ::FindWindow(NULL, TEXT("MessageBoxCaption"));
HWND label = ::GetDlgItem(msgBox, 0xFFFF);
::GetWindowText(label, text, sizeof(text)-1);

Try simulating a copy operation (Ctrl-C), then fetch the text from the clipboard: messageboxes allow copying the whole content that way (if they're properly done).
The OP commented that: that worked, thanks. I might end up with doing it that way. Ideally we wanted to keep our implementation focus independant, but choosing between a dedicated PC and OCR I'd probably go the first route.
Personally I've tested this in Delphi 6 and it comes out looking like this:
---------------------------
Confirm
---------------------------
You are about to close the program
WARNING: Are you sure?
---------------------------
Yes No
---------------------------
Note: This is based on an answer that was proposed by "Stefan" in the comments to the original Question