WinForms ReadOnly TextBox按下Ctrl-R键

Question

I have a C# WinForms sample application, demonstrating interesting key handling issue. That's very simple: there is just a Form and TextBox on it. I set TextBox ReadOnly property to true .

I have the next code in my Form :

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void textBox1_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyData.HasFlag(Keys.R))
        {
            MessageBox.Show("There is 'R' key in KeyDown event");
        }
    }
}

When I press Ctrl - R keys, the MessageBox doesn't show up. But if I set ReadOnly property of TextBox to true , the MessageBox appears. The same thing happens, when I press Shift - R or Alt - R on ReadOnly TextBox .

Any ideas, what is special with ReadOnly TextBox and Ctrl - R combination?

Answer 1

There is a patch in the TextBoxBase.ProcessCmdKey() method , it fixes a problem with certain short-cut keys still modifying the text when the control's ReadOnly property is set. They are Ctrl+R, Ctrl+J, Ctrl+E and Ctrl+L.

Afaik, this patch is a bit too crude, it should only apply to RichTextBox.

This problem is fixable by overriding the TextBox class and restore the normal behavior of these keys. Add a new class to your project and paste the code shown below. Compile. Drop the new control from the top of the toolbox, replacing your original textbox.

using System;
using System.Windows.Forms;

class MyTextBox : TextBox {
    protected override bool ProcessCmdKey(ref Message msg, Keys keyData) {
        if (keyData == (Keys.Control | Keys.R) ||
            keyData == (Keys.Control | Keys.L) ||
            keyData == (Keys.Control | Keys.E) ||
            keyData == (Keys.Control | Keys.J)) return false;
        return base.ProcessCmdKey(ref msg, keyData);
    }
}

Answer 2

It appears this is a known issue. You'd have to ask Microsoft for the why of it... http://social.msdn.microsoft.com/Forums/en-US/941c9759-5531-49fe-9ebb-7fc6d812b0fd/ctrle-not-working-in-a-read-only-text-box?forum=csharplanguage

General advice: If you want to detect a specific character , then use KeyPress() . It is called after translation from the keyboard key to the character set.

private void textBox1_KeyPress(Object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == 'R')
        MessageBox.Show("Hit an 'R'");
}

To handle keyboard "shortcuts", change the test:

if (ModifierKeys == Keys.Control && e.KeyChar == 'R')

Answer 3

You might look at the ShortCutsEnabled property.

As already seen on this post: Why are some textboxes not accepting Control + A shortcut to select all by default

Answer 4

For CTRL+R combination

private void KeyDown(object sender, KeyEventArgs e)
{
  if (e.Control && e.KeyCode == Keys.R)
  {
    //your code
  }
}