Develop Reference

Capturing Ctrl+A shortcut key

I need to capture a kepress combo on the keyboard so i can override the standard function, i've tried the following:
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.Control && e.KeyCode == Keys.A)
{
MessageBox.Show("Hello");
}
}
But when pressing Ctrl+A the message is not triggered. The end aim is to override the windows shortcut 'select all' in a DataGridView within the Form1 to ensure only certain rows are selected when Ctrl+A is pressed in the form window.

First, ensure that Form1 property
KeyPreview = true
Next, do not forget to handle the message (you don't want DataGridView process the message and do SelectAll)
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.Control && e.KeyCode == Keys.A)
{
e.Handled = true; // <- do not pass the event to DataGridView
MessageBox.Show("Hello");
}
}
So you preview KeyDown on the Form1 (KeyPreview = true), perform the required action, and prevent DataGridView from executing select all (e.Handled = true)

In general to handle a shortcut key, you can override ProcessCmdKey. By overriding this method, you can handle the key combination:
protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
if (keyData == (Keys.Control | Keys.A))
{
MessageBox.Show("Control + A");
return true;
}
return base.ProcessCmdKey(ref msg, keyData);
}
Returning true, means it's handled by your code and the key will not pass to the child control. So it's enough to override this method at form level.
But if you are talking specifically about DataGridView to customize the Ctrl + A combination, you can override ProcessDataGridViewKey method of the DataGridView:
public class MyDataGridView : DataGridView
{
protected override bool ProcessDataGridViewKey(KeyEventArgs e)
{
if (e.KeyData == (Keys.A | Keys.Control))
{
MessageBox.Show("Handled");
return true;
}
return base.ProcessDataGridViewKey(e);
}
}

Just for the records: This can be done with KeyPress too, because the Ctrl+Letter keys are "special":
private void Form1_KeyPress(object sender, KeyPressEventArgs e)
{
if(e.KeyChar=='\u0001') //Ctrl+A, B=2, C=3 ...
{
MessageBox.Show("Control + A");
}
}

break button_click event when enter pressed

Is an easy way to cancel click event when user hit enter on button (instead of mouse click on button?)
i have tried with:
private void button3_Click(object sender, EventArgs e)
{
KeyEventArgs ke = e as KeyEventArgs;
if (ke != null)
{
if (ke.KeyCode == Keys.Enter)
{
return;
}
}
}
But ke is null

public void btnClick(object sender, EventArgs e)
{
bool IsMouse = (e is System.Windows.Forms.MouseEventArgs);
// If not mouse, they hit spacebar or enter
}

Yes it will be null. because EventArgs is not KeyEventArgs
KeyEventArgs will be passed as a parameter to KeyDown or KeyUp events. You're messing up things.

You can do something like this
private bool flag = false;
private void button1_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == (char)Keys.Return)
{
flag = true;
}
}
private void button1_Click(object sender, EventArgs e)
{
if (flag)
{
flag = false;
return;
}
//else do original task
}

You can handle KeyPress event for the button and disable or ignore enter key there instead of returning in button click

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
if ((keyData & Keys.KeyCode) == Keys.Enter)
{
SendKeys.Send("{Tab}");
return true;
}
return false;
}

Form1_KeyDown not working as per required

I have taken a link button on my form and on KeyDown event I write as follows to move the link button to left
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Left)
{
linkLabel1.Left = linkLabel1.Left + 5;
}
}
But this is not moving the linklabel as per required, can some one tell where I went wrong
This too didn't work
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
switch (e.KeyCode)
{
case Keys.Left:
linkLabel1.Left = linkLabel1.Left + 5;
break;
default:
return;
}
}

set form1`s KeyPreview = true.
it works.

I think its to do with the interception of events by the linklabel. With the link label present on the form the key down event will not be raised to the form.
Setting KeyPreview to true (on the form) goes someway towards fixing this. You should then get the event raised, though you might still have problems with the arrow keys.
Update:
Ok, this should work, add this:
protected override bool ProcessDialogKey(Keys keyData)
{
if (keyData == Keys.Left)
{
linkLabel1.Left = linkLabel1.Left + 5;
}
return base.ProcessDialogKey(keyData);
}

When you want to move a Control, you have to reconfigure it's Control.Location property.
So simply add or remove some dots form the Location.[X/Y].Property and that's all!
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Left)
{
// have we space?
if(linkLabel1.Location.X >= 4)
// 5 dots to the left side
linkLabel1.Location = new Point(linkLabel1.Location.X - 5, linkLabel1.Location.Y);
}
}
EDIT:
msdn
Location is a Point and a Point has a (x,y) - Coordinate.

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
if (e.KeyCode == Keys.Left)
{
linkLabel1.Left = linkLabel1.Left + 5;
}
return base.ProcessCmdKey(ref msg, keyData);
}

Detect when two keys are pressed at the same time

I have no idea how do this.
I know only how do detect one key:
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.C)
{
MessageBox.Show("C key");
}
}

You have to keep track of keydown/keyup events, and keep a list of all the keys that are currently "down". The keyboard handler can only trigger on individual keys, and it's up to your code to detect/keep track of which ones are down, and if those individual keydown events are close enough to each other to be counted as "together".

put a break point in your key down event and press your two keys together. examine the KeyData of the KeyEventArgs. it will show you what you have to use to detect two keys pressed together. Use some dummy code like this:
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
MessageBox.Show("KeyData is: " + e.KeyData.Tostring());
}
like I have done for shift and r pressed together

As you can see, you can use a timer event with booleans to detect if two keys are pressed:
bool keyup = false;
bool keyleft = false;
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Up)
{
keyup = true;
}
else if (e.KeyCode == Keys.Left)
{
keyleft = true;
}
}
private void Form1_KeyUp(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Up)
{
keyup = false;
}
else if (e.KeyCode == Keys.Left)
{
keyleft = false;
}
}
private void Form1_Load(object sender, EventArgs e)
{
timer1.Start();
}
private void timer1_Tick(object sender, EventArgs e)
{
if (keyleft && keyup)
{
Console.Beep(234, 589);
}
}

Use this:
protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
string keysPressed = keyData.ToString();
// your code goes here
}
This is what I get for Up + Shift: "Up, Shift"

How do I capture the enter key in a windows forms combobox

How do I capture the enter key in a windows forms combo box when the combobox is active?
I've tried to listen to KeyDown and KeyPress and I've created a subclass and overridden ProcessDialogKey, but nothing seems to work.
Any ideas?
/P

Hook up the KeyPress event to a method like this:
protected void myCombo_OnKeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == 13)
{
MessageBox.Show("Enter pressed", "Attention");
}
}
I've tested this in a WinForms application with VS2008 and it works.
If it isn't working for you, please post your code.

In case you define AcceptButton on your form, you cannot listen to Enter key in KeyDown/KeyUp/KeyPress.
In order to check for that, you need to override ProcessCmdKey on FORM:
protected override bool ProcessCmdKey(ref Message msg, Keys keyData) {
if ((this.ActiveControl == myComboBox) && (keyData == Keys.Return)) {
MessageBox.Show("Combo Enter");
return true;
} else {
return base.ProcessCmdKey(ref msg, keyData);
}
}
In this example that would give you message box if you are on combo box and it works as before for all other controls.

or altertatively you can hook up the KeyDown event:
private void comboBox1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Enter)
{
MessageBox.Show("Enter pressed.");
}
}

private void comboBox1_KeyDown( object sender, EventArgs e )
{
if( e.KeyCode == Keys.Enter )
{
// Do something here...
} else Application.DoEvents();
}

Try this:
protected override bool ProcessCmdKey(ref Message msg, Keys k)
{
if (k == Keys.Enter || k == Keys.Return)
{
this.Text = null;
return true;
}
return base.ProcessCmdKey(ref msg, k);
}

It could be that your dialog has a button that's eating the enter key because it's set to be the AcceptButton in the form property.
If that's the case then you solve this like this by unsetting the AcceptButton property when the control gets focus then resetting it back once the control loses focus ( in my code, button1 is the accept button )
private void comboBox1_Enter(object sender, EventArgs e)
{
this.AcceptButton = null;
}
private void comboBox1_Leave(object sender, EventArgs e)
{
this.AcceptButton = button1;
}
private void comboBox1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyData == Keys.Enter)
{
MessageBox.Show("Hello");
}
}
I have to admit not liking my own solution as it seems a little hacky to unset/set the AcceptButton property so if anyone has a better solution then I'd be interested

protected void Form_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == 13) // or Key.Enter or Key.Return
{
MessageBox.Show("Enter pressed", "KeyPress Event");
}
}
Don't forget to set KeyPreview to true on the form.