VB.NET Keypress Events
While messing around with the blog I found that one of the
most viewed pages on here is the VBA Keypress event. If that many people are
looking for it in VBA, there has to be a few who need it in .NET. I use it from
time to time, primarily to handle the pasting of data from the clipboard into a
datagridview, so I will share that as well.
The first piece is the most difficult, not because of
complex code, but for remembering to do it. On your form go to your properties
window and change the KeyPreview property to True. I never remember that part,
and when I do I never remember the name. The help window for the property
states “KeyPreview-Determines whether keyboard events for controls on the form
are registered with the form.” In my own words “it turns on key press events”.
That was the hard part (it will be the next time you try
this), the next part is a little confusing at first. Create a KeyPress event
for your form. For those who don’t know how, there are 2 dropdowns just above
your Public Class Form1 line of code, select (Form1 Events) from the left box,
and KeyPress from the right dropdown.
You may have noticed a KeyDown event as well as the KeyPress
event, there is a lot of confusion about which one to use and why. I will
explain the differences in usage and translation as well as possible because
each has a different purpose, and used in different ways.
Below I will provide a graphic showing which keys trigger
which an event. If you want to remind yourself in the future or have other keys
to test you can create an app with a couple of labels named lblKeyDown and
lblKeyPress and test them yourself with the below.
The form:
Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles Me.KeyDown
lblKeyDown.Text = e.KeyCode
End Sub
Private Sub Form1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles Me.KeyPress
lblKeyPress.Text = "KeyPress" &
e.KeyChar
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
lblKeyDown.Text = ""
lblKeyPress.Text = ""
End Sub
Just run the app and
start smashing keys.
Here is the map, read below about modifiers (shift, control,
alt)
KeyPress and KeyDown
Event Triggers
KeyPress can probably best be summed up by saying that its’
events are triggered by character keys.
Here is a picture of the keys that trigger the events:
KeyDown on the other hand fires and event for every key I
have except the Windows key. One problem that can arise is the use of modifier
keys, for example when you want to copy using control C you get one event for
the control key and another for the C key. However this is easily handled.
One last odd thing, KeyPress returns the actual character of
the key that was pressed while KeyDown returns a KeyCode. For example if you
press the “j” key, KeyPress returns “j”, but KeyDown returns 74. You have to
use e.KeyCode.toString to get the actual value.
For KeyDown you may want to handle modifiers, if you don’t
then A)you won’t know if one was pressed and B)depending on your usage it will
send the modifier as a key when you don’t really want it. This is pretty simple
though, you just use e.Control, e.Shift etc. to determine if the modifier is
pressed. For example say you only want to handle a Control+C, here is how you
do it:
If e.Control = True Then
If e.KeyCode.ToString = "C" Then
MsgBox("Control+C pressed")
End If
End If
That should cover most scenario’s you will need. Now I’ll
show you how to handle the pasting of data to a datagridview.
Paste to Datagridview
Assuming you have a datagridview named datagridview1, and
you have the appropriate columns already added, the following code will paste the
values in your clipboard to the datagridview.
Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles Me.KeyDown
If e.Control = True Then
If e.KeyCode.ToString = "V" Then
PasteClipboard()
End If
End If
End Sub
Private Sub PasteClipboard()
Dim s As String = Clipboard.GetText() 'Get clipboard data as a string
Dim rows() As String = s.Split(ControlChars.NewLine) 'Split into rows
Dim I, j As Integer
Try
For I = 0 To rows.Length - 1
'Add
new row
If Me.DataGridView1.Rows.Count < rows.Length Then Me.DataGridView1.Rows.Add()
'Split
row into cells
Dim bufferCell() As String = rows(i).Split(ControlChars.Tab)
'Copy
to datagrid
For j = 0 To bufferCell.Length - 1
'Remove line feed characters
If
bufferCell(j).ToString.Contains(ControlChars.Lf) Then
bufferCell(j) =
bufferCell(j).ToString.Replace(ControlChars.Lf, "")
End If
Me.DataGridView1.Item(j,
I).Value = bufferCell(j)
Next
Next
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
