catch input from a magnetic card reader to a variable

Question

I can't seem to find a way to catch the input of a magnetic card reader. When it swipes, the input gets into active text editor, like say a notepad.

Unfortunately, the focus on textbox field won't do the trick, because I'm required to make it a label instead of a textbox. Thus, I need a way to catch the input from the USB device to a variable or label instead.

Does anyone knows of a .NET class I could use to do this or any better ideas?

Can't you use the textbox and format it to look like a label? After the input ends, you could make it readonly. — Fernando
– Fernando, Commented Mar 24, 2011 at 1:05
yes it is windows forms, users are not allowed to input manually. so I can't use a textbox — Corbee
– Corbee, Commented Mar 24, 2011 at 1:13
You need to figure out how text gets to notepad by spying on windows events (i.e. use Spy++ from VS tools) and then acting accordingly. Likley Bala R's solution with KeyPress is the right one (drag'n'drop or copy-paste are less likley options, setting text directly with WM_SETTEXT event is another possiblilty). Note that your question is unrelated to USB - removing tag may be good option. — Alexei Levenkov
– Alexei Levenkov, Commented Mar 24, 2011 at 1:24

Bala R · Accepted Answer · 2011-03-24 01:14:51Z

If it's a winforms app you could do

 private void Form1_Load(object sender, EventArgs e) { KeyPreview = true; KeyPress += Form1_KeyPress; } private bool inputToLabel = true; void Form1_KeyPress(object sender, KeyPressEventArgs e) { if (inputToLabel) { label1.Text = label1.Text + e.KeyChar; e.Handled = true; } else { e.Handled = false; } }

and as long as the window has focus, the keypress characters will go to the label's text.

+1 as it is a likley way the program that handles this device pastes text to the editor.

Fun Mun Pieng · Accepted Answer · 2011-03-24 01:29:35Z

I don't think there will be anyway for you to prevent the user from manual input. I suspect the card reader that you have emulates a keyboard. So, to be able to read from the reader, you must receive keyboard input, and keyboard input means the user can type anything they like.

A possible solution is to change your card reader to one that uses an API to read from cards.

If getting a better card reader isn't an option, I think the best method to do this is to have a button. When the button is clicked, open a new form that contains the code @Bala R provided. But in addition, close the form within 1 second from the first key input. This will prevent users from tampering the input manually, but will provide sufficient time for the reader to complete.

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