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.

i.e. 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);
    }        

Solution 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!!!

Solution 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

Solution 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
    }
}

Solution 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);
    }

View more solutions