Edit style textbox

Question

Hello

 
        static bool isEditModeEnabled = false; 
        private static void Txb1_KeyDown(object sender, KeyEventArgs e)
        {
            var txb = (TextBox)sender;         
            if (e.Control && e.KeyCode == Keys.R)
            {
                isEditModeEnabled = !isEditModeEnabled;
                e.Handled = true;
            }
}

  private static void Txb_KeyPress(object sender, KeyPressEventArgs e)
        {
            var txb = (TextBox)sender;
           
            if (isEditModeEnabled)
            {
                int currentPosition = txb.SelectionStart;
                txb.Text = txb.Text.Remove(currentPosition, 1).Insert(currentPosition, e.KeyChar.ToString());
                txb.SelectionStart = currentPosition + 1;
                e.Handled = true;
            }

In the above code , i tried to edit the text whenever the user presses ctrl + r inside a textbox . but when he presses ctrl+k , [] is been replacing as text for no reason and whenever he presses backspace the program crashes . Can some expert please check why is this happening .

Thanks in advance .

Answer 1

private static bool isEditModeEnabled = false;

private void Txb_Enter(object sender, EventArgs e) {
    isEditModeEnabled = false; //clear Flag
}

private static void Txb_KeyDown(object sender, KeyEventArgs e) {
    var txb = (TextBox)sender;
    if (e.Control && e.KeyCode == Keys.R) {
        isEditModeEnabled = !isEditModeEnabled;
        e.Handled = true;
        return;
    }
}

private static void Txb_KeyPress(object sender, KeyPressEventArgs e) {
    var txb = (TextBox)sender;
    if (isEditModeEnabled && IsAllowChar(txb, e.KeyChar)) {
        int currentPosition = txb.SelectionStart;
        string txt = txb.Text;
        if (currentPosition < txt.Length) {
            txt = txt.Remove(currentPosition, 1);
        }
        if (txb.MaxLength == 0 || txt.Length < txb.MaxLength) {
            txb.Text = txt.Insert(currentPosition, e.KeyChar.ToString());
            txb.SelectionStart = currentPosition + 1;
            txb.SelectionLength = 0;
            e.Handled = true;
            return;
        }
    }
}

private static bool IsAllowChar(TextBox txb, char keyChar) {
    if (txb.Multiline) {
        switch (keyChar) {
            case '\r':
            case '\n':
            case '\t':
                return true;
            default:
                if (keyChar  < ' ') {
                    return false;
                }
                break;
        }
    } else {
        if (keyChar < ' ') {
            return false;
        }
    }
    return true;
}

Answer 2

Can't remove when there is no character after the caret position.

if (currentPosition < txb.Text.Length - 1)
{
    txb.Text = txb.Text.Remove(currentPosition, 1).Insert(currentPosition, e.KeyChar.ToString());
}
else
{
    txb.Text = txb.Text.Insert(currentPosition, e.KeyChar.ToString());
}