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Hello !
In a vb.net 2013 application , I have a treeview when I need to have drag and drop operations .
But I have a case when the user begin to drag , but before drop to destination node I need to test something and if a condition is false , the entire operation should undo .
How can I do this ?
Thank you !
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It would be easier if you showed your code, so hope this helps.
The normal process is in the DragEnter event you set e.effects = to the drag and drop you will allow (move, copy etc). Then in the DragDrop event determine your condition and set e.Effect = DragDropEffects.None if it is not allowed, else execute the drop code.
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can i use wavelet transform to inhance but using the visual basic not math lab
i am student i donot know if i can use this way in vb
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Sure, you just have to implement the transform yourself in code.
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Would it be hard for someone with no programming knowledge to make an application that simply disables drag from a mouse when you hold left click or just left click in general.
With the option to hold a set key down to momentarily enable leftclick-dragging until you release the key.
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Yes it would be very hard; especially in Visual Basic.
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Don't worry i found a resolution. Thanks.
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Hello !
Is there any way to use and manage an usb barcode reader in a vb.net program ?
What I want to do is :
-- Distinguish reading from barcode reader and typing from keyboard
-- Allow or deny displaying the barcode in a textbox after is read ( I mean when that textbox is focused and active at that moment )
--- Capture the barcode that is read even when no textbox is currently focused or active control at that moment ( I mean when a specific form is open , and a read from barcode reader was made , I should be able to capture the barcode in a variable )
Thank you !
Update
1) Actually , I've read somewhere on internet that to distinguish between reading from barcode reader and typing on keyboard is to keep track on keystrokes timing , for example if a stream of characters are read in less than 100ms ( or another reasonable time) then this mean a barcode reader was made. But I don't know how can I do this ?
2) About the reading in background when no textbox is focused , I've found this article : https://msdn.microsoft.com/en-us/library/ms171538%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396 . Do you think that catching a barcode read at the form level , before reaching the control can help resolve this ?
modified 21-Oct-16 0:05am.
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This has nothing to do with Visual Basic. You are asking for information on how your device works. That information should be in the manufacturer's documents.
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We're talking for general usb barcode readers that act like a keyboard.
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Then the same applies as for any keyboard.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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Yes, and the behaviour of the barcode reader is specific to its design & manufacture. So you still need to read the manual to see how it presents itself and its data.
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What about programs that can work with any kind of usb barcode readers ? so they are general and what they need is only to plug the barcode reader.
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Yes, and what happens then?
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The barcode reader is working as expected.
I've seen some programs ( of course I don't have the code ) that can use any type of USB barcode readers ( without any special configuration ) and can distinguish between 2 modes ( for example focusing a textbox when I type with keyboard nothing is displayed , when I read with barcode reader the barcode is displayed ). And also if I focus a listbox or another control in the form, and read with barcode reader , the barcode is read and displayed in the right textbox without focusing it.And I've tested these programs even with cheap no name Chinese barcode readers and always work perfectly.
So it seems a way should exist.
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desanti wrote: So it seems a way should exist.
Simple; learn C++ and write a generic device driver.
..but in VB.NET, you are limited to what the software that is installed for the device allows you to do.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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These are USB barcode readers that are configured to act like keyboards. No software are needed to install for these devices. Windows has that "Generic drivers" built in.So I can plug different kinds of these barcode readers , at the same Pc and they use the same driver built in on windows.
So these barcode readers are like keyboards with only 1 difference : They can "type" much more chars at a small time compared with typing on keyboard.
I hope that someone can help me working on this idea.
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Yes, Windows already has multiple generic device-drivers. The functionality provided is exactly that, it fits most needs.
If you need more, you contact the manufacturer and see if they have an SDK;
..but from VB? Good luck there 
Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
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Then those programs must be communicating direct to the device(s) via the USB interface. Alternatively, as Dave K already suggested, the device sends extra data to identify itself. Google (as usual) is the place to start your research.
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I've tested and it seems that these barcode readers only send a list of chars and an "ENTER" at the end. So no special characters.
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No , because even on normal keyboard I can write and press ENTER at the end. How to distinguish that was from keyboard or from Barcode reader ?
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There are multiple types of barcode readers. What you're talking about is a "keyboard wedge" type that, as you already know, act like a keyboard.
But, usually they are programmable to prepend and/or append character data to the barcode it reads. This allows applications to add an "attention sequence" to the data it's "keying" into your application. Typically, your application looks for this data coming from the keyboard and can use that data to know that the next characters are part of the barcode until it sees the appended sequence.
This makes it possible to use the data WITHOUT having to know which "keyboard" the data came from. THIS IS WHY YOU READ THE DOCUMENTATION ON THE DEVICE YOU'RE USING!
There are also other interface types, such as Ethernet-based devices, that you can code against. But, again, this is where you read the documentation on your device.
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Option 1 is a HUGE pain in the ass to implement and isn't reliable.
Option 2 is how this is normally done in a Windows Forms app.
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