/// <summary>
/// Applies format and range rules as the text changes.
/// </summary>
private void OnTextChanged(object sender, TextChangedEventArgs args)
{
// Save selection position relative to right edge
var originalTextLength = _originalText.Length;
var selectionOffset = originalTextLength - _originalSelectionStart;
// Call before event handler
var change = new DynamicTextChangedEventArgs(Text, _originalText);
OnBeforeTextChanged(sender, change);
// Adjust text value when changed by event handler
if (Text != change.Text)
{
Text = _originalText = change.Text;
}
_originalText = Text;
// Restore selection
var textLength = change.Text.Length;
var selectionStart = textLength - selectionOffset;
if (selectionStart < 0)
{
selectionStart = 0;
}
else if (selectionStart > textLength)
{
selectionStart = textLength;
}
if (SelectionStart != selectionStart)
{
SelectionStart = selectionStart;
}
_originalSelectionStart = selectionStart;
// Update cursor
LayoutCursor();
// Call after event handlers
OnAfterTextChanged(sender, change);
}
/// <summary>
/// Called before the base text box changed event is processed but this class, but after the core text box has
/// already processed a change (because it provides no text change handler itself to override).
/// This class performs trimming or padding here, so must be called when overridden to retain this functionality.
/// </summary>
protected virtual void OnBeforeTextChanged(object sender, DynamicTextChangedEventArgs args)
{
// Trim text when too long
var text = args.Text;
var maxLength = MaxLength;
if (maxLength > 0 && text.Length > maxLength)
{
// Trim text
text = text.Substring(0, maxLength);
}
// Pad text when enabled and too short
var minLength = MinLength;
if (minLength > 0 && text.Length < MinLength && PadChar.HasValue)
{
text = text.PadLeft(minLength, PadChar.Value);
}
// Return result
args.Text = text;
}
/// <summary>
/// Strips non-numeric characters according to <see cref="NumberBase"/> before processing text changes.
/// </summary>
protected override void OnBeforeTextChanged(object sender, DynamicTextChangedEventArgs args)
{
// Apply decimal sign rules
var originalText = args.OriginalText;
var textValue = args.Text;
bool?sign = null;
if (NumberBase == NumericTextBoxNumberBase.Decimal && NumberSigned)
{
// Detect sign
if (textValue.StartsWith("+", StringComparison.OrdinalIgnoreCase))
{
sign = true;
}
else if (textValue.StartsWith("-", StringComparison.OrdinalIgnoreCase))
{
sign = false;
}
// Apply sign rules
if (sign.HasValue)
{
// Remove sign when only remaining character
if (textValue.Length == 1)
{
sign = null;
}
// Prevent selection of sign itself
else if (SelectionStart == 0)
{
SelectionStart = 1;
}
}
}
// Strip invalid characters
var validChars = GetValidNumberChars((int)NumberBase);
var text = "";
foreach (var textChar in args.Text)
{
// Allow sign as first char
if (sign.HasValue && text.Length == 0 && (textChar == '+' || textChar == '-'))
{
text += textChar;
}
else
{
// Allow only valid number chars for rest of string
if (validChars.IndexOf(textChar.ToString(), StringComparison.OrdinalIgnoreCase) >= 0)
{
// Add valid char with uppercase correction if necessary
if (Char.IsLetter(textChar) && !Char.IsUpper(textChar))
{
// Correct lower to upper case
text += Char.ToUpperInvariant(textChar);
}
else
{
// No change necessary
text += textChar;
}
}
else
{
// Skip or pad invalid char
if (PadChar.HasValue)
{
text += PadChar.Value;
}
}
}
}
// Validate number when set (format and sign, minimum and maximum)
if (!String.IsNullOrEmpty(text))
{
var numberBase = (int)NumberBase;
if (!Number.TryParse(text, numberBase, out Number value) || value < NumberMin || value > NumberMax)
{
// Discard changes when invalid
text = originalText;
}
}
// Call base class to trim or pad remaining text
args.Text = text;
base.OnBeforeTextChanged(sender, args);
}
/// <summary>
/// Called after the base text box changed event has been processed.
/// </summary>
protected virtual void OnAfterTextChanged(object sender, DynamicTextChangedEventArgs args)
{
}