Detecting ctrl+v on key press

Question

I am using text box keypress event to handle only selected inputs. Basically the textbox allow user to input values where it can be calculated.

ie you can type (5*5)- (10/5) .

The current method check like Convert.ToChar("*")==e.KeyChar etc...

At the moment it doesn't allow user to copy paste values.

Is there anyway that can detect the ctrl+v on keypress event?

Update

What I am doing at the moment

   static IEnumerable<char> ValidFiancialCharacters
       {
           get
           {
               if(_validFiancialCharacters==null)
               {
                 _validFiancialCharacters = new List<char>();

                 _validFiancialCharacters.Add(Convert.ToChar("0"));
                 _validFiancialCharacters.Add(Convert.ToChar("1"));
                 _validFiancialCharacters.Add(Convert.ToChar("2"));
                 // till 9 and
                  _validFiancialCharacters.Add(Convert.ToChar("+"));
                  _validFiancialCharacters.Add(Convert.ToChar("-"));
                  _validFiancialCharacters.Add(Convert.ToChar("/"));
                  //and some other
                }
                return _validFiancialCharacters;
             }
       }


 public static bool ValidateInput(KeyPressEventArgs e)
   {
       if (ValidFiancialCharacters.Any(chr => chr == e.KeyChar))
       {
           e.Handled = false;
       }
       else
       {
           e.Handled = true;
       }
       return e.Handled;
   }

And in the keypress

   private void txtRate_KeyPress(object sender, KeyPressEventArgs e)
    {
        NumberExtension.ValidateInput(e);
    }        

Answer 1

If you need to handle both, can be done using the similar approach

Have a look at Key Codes . You can detect what ever the key been pressed

so..

Create a list containing all the inputs you need

 public List<int> KeyCodes = new List<int>() { 8, 17, 37, 39.....etc}; 

and use the KeyDown event and use KeyEventArgs.SuppressKeyPress property

private void Txt1_KeyDown(object sender, KeyEventArgs e)
{
    if (KeyCodes.Contains(e.KeyValue) || (e.KeyCode==Keys.V && e.Control))
        e.SuppressKeyPress = false;
    else 
        e.SuppressKeyPress=true;
}

You might need to validate the copy pasted value in leave event , since user can paste anything!!!

Answer 2

Just look at the Modifiers propertie in you KeyDown or KeyUp event for Keys.Control

Modifiers Gets the modifier flags for a KeyDown or KeyUp event. The flags indicate which combination of CTRL, SHIFT, and ALT keys was pressed.

Sample

KeyDown

 this.myTextBox.KeyDown += new KeyEventHandler(myTextBox_KeyDown);

 private void myTextBox_KeyDown(object sender, KeyEventArgs e)
 {
      if (e.KeyCode == Keys.V && e.Modifiers == Keys.Control)
      {
            MessageBox.Show("Hello world");
      }
  }

or KeyUp

 this.myTextBox.KeyUp += new KeyEventHandler(myTextBox_KeyUp);

 private void myTextBox_KeyUp(object sender, KeyEventArgs e)
 {
      if (e.KeyCode == Keys.V && e.Modifiers == Keys.Control)
      {
            MessageBox.Show("Hello world");
      }
  }

Update

To allow only certain inputs you can use the KeyPress event.

this.myTextBox.KeyPress += new KeyPressEventHandler(this.myTextBox_KeyPress);

private void myTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
    int i;
    if (int.TryParse(e.KeyChar.ToString(), out i) || 
        e.KeyChar == '(' ||
        e.KeyChar == ')' ||
        e.KeyChar == '.' ||
        e.KeyChar == '*' ||
        e.KeyChar == '+' ||
        e.KeyChar == '-' ||
        e.KeyChar == '/'
        // add some more)
    {

    } else e.Handled = true; // dont allow other inputs
}

More Information

• MSDN - KeyEventArgs Class
• MSDN - Control.KeyDown Event
• MSDN - Control.KeyUp Event

Answer 3

KeyPress event doesn't catch "Ctrl + V" for some reason. Use KeyDown event:

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Control && e.KeyCode == Keys.V)
    {
        //Ctrl + V
    }
}

or

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyData == (Keys.Control | Keys.V))
    {
        //Ctrl + V
    }
}

Answer 4

The Ctrl+V sequence can be catched by KeyPressEvent.
You just cannot check it by the following :

(Keys)e.KeyChar == Keys.V && Control.ModifierKeys == Keys.Control <br>

You must use:

(int)e.KeyChar==22 && Control.ModifierKeys == Keys.Control <br>

because the keybord generates the ASCII=22 (synchronous idle).
The following example enables TextBox to accept +- amounts with comma separator and allows pasting by Ctrl+V

protected override void OnKeyPress(KeyPressEventArgs e)
{
    if (!( char.IsNumber(e.KeyChar) ||
         ((Keys)e.KeyChar == Keys.Back) ||
         (e.KeyChar == ',') ||
         (e.KeyChar == '-') ||
         ((int)e.KeyChar==22 && Control.ModifierKeys == Keys.Control)
        ))
        {
            e.Handled = true;
        }
        if (e.KeyChar == ',' && base.Text.IndexOf(',') > 0)
        {
            e.Handled = true;
        }
        base.OnKeyPress(e);
    }

Answer 5

You should use KeyDown or KeyUp, because the KeyPress event is not raised by the CTRL button but only by "character" buttons. If you use the KeyDown event you can detect ctrl+v by checking:

if (e.Control && e.KeyCode == Keys.V)
{
    ...
}