Validate textbox on key down event to accept only numbers in silverlight 4

Question

I need a validation to check whether key pressed down is numeric or not. I tried with different code but they cant help me out.In the textbox if the user press Shift+numbers it displays special characters like !,@,# ...... I need to validate the Shift + key down event .

//Code

    private void txtNumericTextbox_KeyDown(object sender, KeyEventArgs e)
            {
                try
                {
                    if (e.Key < Key.D0 || e.Key > Key.D9)
                    {
                        if (e.Key < Key.NumPad0 || e.Key > Key.NumPad9)
                        {
                            if (e.Key != Key.Back)
                            {
                                txtNumericTextbox_.BorderBrush = new SolidColorBrush(Colors.Red);
                                lblErrorMessage.Visibility = Visibility.Visible;
                                lblErrorMessage.Text = "Please Enter Numbers Only";
                            }
                            else
                            {
                                txtNumericTextbox_.BorderBrush = new SolidColorBrush(Colors.DarkGray);
                                lblErrorMessage.Visibility = Visibility.Collapsed;
                                lblErrorMessage.Text = "";
                            }
                        }
                    }
                 }
             }

How can I achieve that?

Answer 1

You can use the ModifierKeys property on control to determine if the shift key is being held.

//Code

Use this to accept only numeric values. Event you can choose textBox1_KeyDown nonnumberenter = false;

            if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9)
            {
                if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
                {
                    if (e.KeyCode != Keys.Back)
                    {
                        nonnumberenter = true;
                        string abc = "Please enter numbers only.";
                        DialogResult result1 = MessageBox.Show(abc.ToString(), "Validate numbers", MessageBoxButtons.OK);
                    }
                }
            }
            if (Control.ModifierKeys == Keys.Shift)
            {
                nonnumberenter = true;
                string abc = "Please enter numbers only.";
                DialogResult result1 = MessageBox.Show(abc.ToString(), "Validate numbers", MessageBoxButtons.OK);

            }

Use this to accept only characters. Event you can choose textBox1_KeyPress

if (Char.IsNumber(e.KeyChar) || Char.IsSymbol(e.KeyChar) || Char.IsWhiteSpace(e.KeyChar) || Char.IsPunctuation(e.KeyChar))
            {
                MessageBox.Show("Only Char are allowed");
                e.Handled = true;
            }

Hope this helps.

Answer 2

You can use text box key press event

private void txt_KeyPress(object sender, KeyPressEventArgs e)
    {
        if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) )
        {
            e.Handled = true;
        }
    }

Answer 3

I was looking for the same thing: . 。 However, I did not find any e.KeyCode on my _KeyDown event, so I adapted Kumar's code to suit my needs, and am sharing with you, should it be more fitting to you: Use e.Handled = true to cancel the input of that character.

    private void textBox1_KeyDown(object sender, KeyEventArgs e)
    {
        switch (e.Key)
        {
            case Key.NumPad0:
            case Key.NumPad1:
            case Key.NumPad2:
            case Key.NumPad3:
            case Key.NumPad4:
            case Key.NumPad5:
            case Key.NumPad6:
            case Key.NumPad7:
            case Key.NumPad8:
            case Key.NumPad9:
            case Key.D0:
            case Key.D1:
            case Key.D2:
            case Key.D3:
            case Key.D4:
            case Key.D5:
            case Key.D6:
            case Key.D7:
            case Key.D8:
            case Key.D9:
                break;
            default:
                e.Handled = true;
                break;
        }
    }