Allow copy/paste feature to the textbox in windows forms

December 5, 2023

My application contains a textbox where we need not to allow special characters.I had written the logic in Keypress event of textbox. But the textbox is not allowing to copy/paste feature.How can I make to allow the copy/paste feature from the following code in keypress event.Mycode is as follows :

private void textBox4_KeyPress(object sender, KeyPressEventArgs e)
{
    if(comboBox10.Text == "Abc")
    {
        if (e.KeyChar != (char)Keys.Back && !char.IsSeparator(e.KeyChar) && !char.IsLetter(e.KeyChar) && !char.IsDigit(e.KeyChar))
        {
            MessageBox.Show("Special characters are not allowed");
            e.Handled = true;
        }
        //e.Handled = e.KeyChar != (char)Keys.Back && !char.IsSeparator(e.KeyChar) && !char.IsLetter(e.KeyChar) && !char.IsDigit(e.KeyChar);
    }
}

As of now the above code is working fine for not allowing the special characters but, When I press ctrl+v the messagebox is displaying.

>Solution :

private void textBox4_KeyPress(object sender, KeyPressEventArgs e)
{
    // Check if Ctrl pressed
    if ((Control.ModifierKeys & Keys.Control) == Keys.Control)
    {
        return; // Allow Copy/Paste
    }

    if (comboBox10.Text == "Abc")
    {
        if (e.KeyChar != (char)Keys.Back && !char.IsSeparator(e.KeyChar) && !char.IsLetter(e.KeyChar) && !char.IsDigit(e.KeyChar))
        {
            MessageBox.Show("Special characters are not allowed");
            e.Handled = true;
        }
    }
}