CODEWITHSUNDEEP
c#winformsrichtextboxkeydown
ferc
ferc

Reputation: 558

Ignore KeyDown if the text of a RichTextBox won't change

I need to determine whether a key, when it is pressed, will change the control's text or not; I need to ignore key presses like Ctrl+Z or Esc, but I need to know which key was pressed if the text changed.

Is there any way to know that in the KeyDown event? Currently, I'm using a flag, set on KeyDown and checked on TextChanged, but I was wondering if there is a better way?

Upvotes: 3

Views: 4056

Answers (3)

DROP TABLE users
DROP TABLE users

Reputation: 1955

You could catch the KeyPress event on the text box and if it is a valid key you would set e.handled = false and if it was a bad key you would set e.handled = true.

example from: here

private void keypressed(Object o, KeyPressEventArgs e)
    {
        // The keypressed method uses the KeyChar property to check  
        // whether the ENTER key is pressed.  

        // If the ENTER key is pressed, the Handled property is set to true,  
        // to indicate the event is handled. 
        if (e.KeyChar == (char)Keys.Return)
        {
            e.Handled = true;
        }
    }

Upvotes: 1

Sriram Sakthivel
Sriram Sakthivel

Reputation: 73442

You're looking for Char.IsControl

private Keys lastKey = Keys.None;
private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    lastKey = e.KeyData;
}

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (Char.IsControl(e.KeyChar))
    {
        e.Handled = true;//prevent this key press
        Keys pressedKey = this.lastKey;
        //Do your stuff with pressedKey  here
    }
}

Upvotes: 4

Alireza
Alireza

Reputation: 10476

There are some keys which produce a Control char but they also change the text, for example BackSpace. They have another difficulty: if the textbox is empty, pressing them (for example BackSpace) doesn't change the text; so it breaks the previous rule. So Control characters are not naive to deal with and build a rule upon.

Moreover, consider Ctrl + C or Shift + Insert or similar cases. The 'C' key is somehow seductive; it is like pressing 'C' changes the text but if it was pressed with 'Ctrl', it actually didn't change the text. We should check the Modifiers.

Perhaps you can find other difficulties to deal with and I think the flag approach is good enough.

Upvotes: 0

Related Questions