如何使用 C# 禁用文本框上的复制、粘贴和删除功能

Question

有人可以建议如何使用 C# 在 WinForms 中的文本框中处理剪切、复制和粘贴事件吗？

Answer 1

在 WinForms 中，禁用文本框上的剪切、复制和粘贴功能的最简单方法是将 ShortcutsEnabled 属性设置为 false。

Answer 2

You'd have to subclass the textbox and then override the WndProc method to intercept the windows messages before the control does.

Here's an example that illustrates a TextBox that intercepts the WM_PASTE message.

And for reference, here's the definition of the message constants:

• WM_PASTE
• WM_COPY
• WM_CUT

You'd simply ignore the inbound message, like so:

protected override void WndProc(ref Message m)
{
   if (m.Msg == WM_PASTE || m.Msg == WM_COPY || m.Msg == WM_CUT)
   {
      // ignore input if it was from a keyboard shortcut
      // or a Menu command
   }
   else
   {
      // handle the windows message normally
      base.WndProc(ref m);
   }
}

Answer 3

Suppose you have a TextBox named textbox1 . It sounds like you want to disable the cut, copy and paste functionality of a TextBox.

Try this quick and dirty proof of concept snippet:

private void Form1_Load(object sender, EventArgs e)
{
    ContextMenu _blankContextMenu = new ContextMenu();
    textBox1.ContextMenu = _blankContextMenu; 
}


private const Keys CopyKeys = Keys.Control | Keys.C;
private const Keys PasteKeys = Keys.Control | Keys.V;

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
    if ((keyData == CopyKeys) || (keyData == PasteKeys))
    {
        return true;
    }
    else
    {
        return base.ProcessCmdKey(ref msg, keyData);
    }
} 

Answer 4

To prevent users to copy/paste using the keyboard set ShortcutsEnabled property to false. To prevent users to copy/paste from the context menu set ContextMenu property to new ContextMenu().

if (copyPasteEnabled) {
   textBox1.ShortcutsEnabled = true;
   textBox1.ContextMenu = null;
} else {
   textBox1.ShortcutsEnabled = false;
   textBox1.ContextMenu = new ContextMenu();
}

Answer 5

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.Enter)
    {
        e.SuppressKeyPress = true;
    }

    if (e.Control == true)
    {
        switch (e.KeyCode)
        {
            case Keys.C:
            case Keys.P:
            case Keys.X:
                e.Handled = true;
                textBox1.SelectionLength = 0;
                break;
        }
    }
}

private void textBox1_Enter(object sender, EventArgs e)
{
    System.Windows.Forms.Clipboard.Clear();
}

Answer 6

int cusorposition = m_TextBox1.SelectionStart;
if (TextBox1.Text[0] == ' ')
{
//Trim Spaces at beginning.
      m_TextBox1.Text = m_TextBox1.Text.TrimStart(' ');
      m_TextBox1.Text = m_TextBox1.Text.TrimEnd(' ');
      m_TextBox1.SelectionStart = cusorposition ;
}

---

Hi I found a way how to get the current cursor position instead of handling cut, copy and Paste event in a text box named TextBox1.Here in the above I am keeping the backup of current Cursor Position and after trimming the extra spaces from the starting and from end position I am reassigning the current cursor position.

Thanks to all who helped me to fix this problem.