Develop Reference

How to validate TextBox to allow only 1 decimal point - Windows Phone 8

I want to validate TextBox to allow only 1 decimal point and up to 2 decimal places after it. For number validate only, i am using InputScope="Number", but it can not avoid pasting letters, so i need any validation for paste too (or just disable pasting). For example the user must be able to insert numbers like 23, 23.1, 23.12 and NOT 23.123, 23.1.2 etc.

private void tb1_KeyDown(object sender, KeyRoutedEventArgs e)
{
if (e.Key >= Windows.System.VirtualKey.Number0 && e.Key <= Windows.System.VirtualKey.Number9 || e.Key == Windows.System.VirtualKey.Decimal || e.Key == Windows.System.VirtualKey.GamepadY)
{
string strkey = e.Key.ToString().Substring(e.Key.ToString().Length - 1, e.Key.ToString().Length - (e.Key.ToString().Length - 1));
if (e.Key >= Windows.System.VirtualKey.Number0 && e.Key <= Windows.System.VirtualKey.Number9)
{
TextBox tb = sender as TextBox;
int cursorPosLeft = tb.SelectionStart;
int cursorPosRight = tb.SelectionStart + tb.SelectionLength;
string result1 = tb.Text.Substring(0, cursorPosLeft) + strkey + tb.Text.Substring(cursorPosRight);
string[] parts = result1.Split('.');
if (parts.Length > 1)
{
if (parts[1].Length > 2 || parts.Length > 2)
{
e.Handled = true;
}
}
}
if (((TextBox)sender).Text.Contains(".") && e.Key == Windows.System.VirtualKey.Decimal)
{
e.Handled = true;
}
}
else
{
e.Handled = true;
}
if (e.Key >= Windows.System.VirtualKey.A && e.Key <= Windows.System.VirtualKey.Z ||
e.Key == Windows.System.VirtualKey.Space)
{
e.Handled = true;
}
}

How to disable certain combination keys (eg. Shift + "certain number key")

I'm created a telephone keypad which consists of 0-9 plus hash key (#) and star key (*). I was able to disable other keys except those number keys so that when user type in the textbox provided, it will only allow number keys. Since # is the combination of Shift+3 and * is the combination of Shift+8, my problem is I can't disable other combination key except those two. So, is there any way to handle this problem in order to just allow Shift+3 and Shift+8 only?
private void NumDisplayBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
//Determine whether the keystroke is a number from the top of the keyboard
if (e.Key < Key.D0 || e.Key > Key.D9)
//Determine whether the keystroke is a number from the keypad
if (e.Key < Key.NumPad0 || e.Key > Key.NumPad9)
e.Handled = true;
if (e.Key == Key.Space) //Disable the space key
e.Handled = true;
//Enable the following keys
if (e.Key == Key.Back || e.Key == Key.Delete || e.Key == Key.Left || e.Key == Key.Right)
e.Handled = false;
//Determine whether the keystroke is # or *
if ((Keyboard.Modifiers == ModifierKeys.Control) && (e.Key == Key.D3))
e.Handled = false;
}

WPF Key is digit or number

I have previewKeyDown method in my window, and I'd like to know that pressed key is only A-Z letter or 1-0 number (without anyF1..12, enter, ctrl, alt etc - just letter or number).
I've tried Char.IsLetter, but i need to give the char, so e.key.ToString()[0] doesn't work, because it is almost everytime a letter.

Something like this will do:
if ((e.Key >= Key.A && e.Key <= Key.Z) || (e.Key >= Key.D0 && e.Key <= Key.D9) || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9))
Of course you will also have to check that no modifier keys like CTRL are pressed according to your requirements.

e.Key is giving you a member of the enum System.Windows.Input.Key
You should be able to do the following to determine whether it is a letter or a number:
var isNumber = e.Key >= Key.D0 && e.Key <= Key.D9;
var isLetter = e.Key >= Key.A && e.Key <= Key.Z;

In your specific case the answer provided by Jon and Jeffery is probably best, however if you need to test your string for some other letter/number logic then you can use the KeyConverter class to convert a System.Windows.Input.Key to a string
var strKey = new KeyConverter().ConvertToString(e.Key);
You'll still need to check to see if any modifier keys are being held down (Shift, Ctrl, and Alt), and it should also be noted that this only works for Letters and Numbers. Special characters (such as commas, quotes, etc) will get displayed the same as e.Key.ToString()

try this, it works.
private void txbNumber_KeyDown(object sender, KeyEventArgs e)
{
if (e.Key >= Key.D0 && e.Key <= Key.D9) ; // it`s number
else if (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) ; // it`s number
else if (e.Key == Key.Escape || e.Key == Key.Tab || e.Key == Key.CapsLock || e.Key == Key.LeftShift || e.Key == Key.LeftCtrl ||
e.Key == Key.LWin || e.Key == Key.LeftAlt || e.Key == Key.RightAlt || e.Key == Key.RightCtrl || e.Key == Key.RightShift ||
e.Key == Key.Left || e.Key == Key.Up || e.Key == Key.Down || e.Key == Key.Right || e.Key == Key.Return || e.Key == Key.Delete ||
e.Key == Key.System) ; // it`s a system key (add other key here if you want to allow)
else
e.Handled = true; // the key will sappressed
}

Add a reference to Microsoft.VisualBasic and use the VB IsNumeric function, combined with char.IsLetter().

bit of a cludge but it works :)
private void TextBox_KeyDown(object sender, KeyEventArgs e)
{
Regex R = new Regex("^([A-Z]|[0-9]){1}$");
var strKey = new KeyConverter().ConvertToString(e.Key);
if(strKey.Length > 1 )
{
strKey = strKey.Replace("NumPad", "").Replace("D", "");
}
if (strKey.Length == 1)
{
if (!R.IsMatch(strKey))
{
e.Handled = true;
}
}
else
{
e.Handled = true;
}
}

Can you put some code to show what you intend? Shouldn't this work for you
if(e.key.ToString().Length==1)
`Char.IsLetter(e.key.ToString()[0])`
else
//

detect Ctrl + Enter

(using WPF)
i try to detect when Ctrl + Enter gets hit.
so i tried this code:
if (e.Key == Key.Return && (e.Key == Key.LeftCtrl || e.Key == Key.RightCtrl))
{
//Do Something
}
Obviously this is not correct, as it does not work.
Could anyone help me out, explaining what the right way should be ?
thanx

Obviously e.Key can't be equal to more than one different value in the same event.
You need to handle one of the events that uses KeyEventArgs, there you'll find properties such as Control and Modifiers that will help you detect combinations.
The KeyPress event, which uses KeyPressEventArgs, just doesn't have sufficient information.
Drat, you said WPF didn't you. It looks like you need e.KeyboardDevice.Modifiers.

I think you need a SpecialKey Handler.
I googled a bit a found a solution here.
Following code from the referred link may solve your problem:
void SpecialKeyHandler(object sender, KeyEventArgs e)
{
// Ctrl + N
if ((Keyboard.Modifiers == ModifierKeys.Control) && (e.Key == Key.N))
{
MessageBox.Show("New");
}
// Ctrl + O
if ((Keyboard.Modifiers == ModifierKeys.Control) && (e.Key == Key.O))
{
MessageBox.Show("Open");
}
// Ctrl + S
if ((Keyboard.Modifiers == ModifierKeys.Control) && (e.Key == Key.S))
{
MessageBox.Show("Save");
}
// Ctrl + Alt + I
if ((Keyboard.Modifiers == (ModifierKeys.Alt | ModifierKeys.Control)) && (e.Key == Key.I))
{
MessageBox.Show("Ctrl + Alt + I");
}
}

if (e.Modifiers == Keys.Control && e.KeyCode == Keys.Enter)

if (e.KeyChar == 10)
{
///Code
}
Or
if ((Char)e.KeyChar == '\n')
{
///Code
}

Silverlight textbox to accept only decimals

I have a Silverlight app with a textbox whose input I want to limit to decimal numbers only. Searching the web I came across the following possible solution (curiously in different places with different people claiming authorship of the same lines of code)
It appears to work well except that after at least 1 numeral has been entered it will then allow the letter 'd' in either upper or lower case to be entered, I can't figure out why that is and thus can't figure out how to prevent that from happening. Could anyone please provide a solution. Many thanks.
private void Unit_KeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Tab)
{
}
var thisKeyStr = "";
if (e.PlatformKeyCode == 190 || e.PlatformKeyCode == 110)
{
thisKeyStr = ".";
}
else
{
thisKeyStr = e.Key.ToString().Replace("D", "").Replace("NumPad", "");
}
var s = (sender as TextBox).Text + thisKeyStr;
var rStr = "^[0-9]+[.]?[0-9]*$";
var r = new Regex(rStr, RegexOptions.IgnoreCase);
e.Handled = !r.IsMatch(s);
}

You could try the following:
Replace the else with else if (e.Key != Key.D) or
set the Handled property like this:
e.Handled = !r.IsMatch(s) || string.IsNullOrEmpty(thisKeyStr);
// also possible:
e.Handled = !r.IsMatch(s) || e.Key == Key.D;

here is a easier code optimized. NO object creation; NO string comparision and NO regex validation
private static void TextBox_KeyDown(object sender, KeyEventArgs e)
{
//platform code for Hyphen which is not same as Subtract symbol but in our case both give same meaning
const int KEYCODE_Hyphen_OnKeyboard = 189;
const int KEYCODE_Dot_OnKeyboard = 190;
const int KEYCODE_Dot_OnNumericKeyPad = 110;
e.Handled = !(
(!( //No modifier key must be pressed
(Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift
|| (Keyboard.Modifiers & ModifierKeys.Control) == ModifierKeys.Control
|| (Keyboard.Modifiers & ModifierKeys.Alt) == ModifierKeys.Alt
)
&& ( //only these keys are supported
(e.Key >= Key.D0 && e.Key <= Key.D9) || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9)
|| e.Key == Key.Subtract || e.Key == Key.Add || e.Key == Key.Decimal
|| e.Key == Key.Home || e.Key == Key.End || e.Key == Key.Delete
|| e.Key == Key.Tab || e.Key == Key.Enter || e.Key == Key.Escape || e.Key == Key.Back
|| (e.Key == Key.Unknown && (
e.PlatformKeyCode == KEYCODE_Hyphen_OnKeyboard
|| e.PlatformKeyCode == KEYCODE_Dot_OnKeyboard || e.PlatformKeyCode == KEYCODE_Dot_OnNumericKeyPad
)
)
)
)
);
}

private void TextBox_KeyDown(object sender, KeyEventArgs e)
{
bool isDigit = e.Key >= Key.D0 && e.Key < Key.D9 || e.Key == Key.NumPad0 || e.Key == Key.NumPad1 || e.Key == Key.NumPad2 || e.Key == Key.NumPad3 || e.Key == Key.NumPad4 || e.Key == Key.NumPad5 || e.Key == Key.NumPad6 ||
e.Key == Key.NumPad7 || e.Key == Key.NumPad8 || e.Key == Key.NumPad9 ||e.Key == Key.Back || e.Key == Key.Delete || e.Key == Key.Left || e.Key == Key.Right;
if (isDigit) { }
else
e.Handled = true;
}