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using System;
using System.Globalization;
using System.Threading;
using WpfEx.Utils;
namespace WpfEx.AttachedBehaviors
{
/// <summary>
/// Helper class that validates text box input for double values.
/// </summary>
internal static class TextBoxDoubleValidator
{
private static readonly ThreadLocal<NumberFormatInfo> _numbersFormat = new ThreadLocal<NumberFormatInfo>(
() => Thread.CurrentThread.CurrentCulture.NumberFormat);
/// <summary>
/// Returns true if input <param name="text"/> is accepted by IsDouble text box.
/// </summary>
public static bool IsValid(string text)
{
// First corner case: null or empty string is a valid text in our case
if (text.IsNullOrEmpty())
return true;
// '.', '+', '-', '+.' or '-.' - are invalid doubles, but we should accept them
// because user can continue typeing correct value (like .1, +1, -0.12, +.1, -.2)
if (text == _numbersFormat.Value.NumberDecimalSeparator ||
text == _numbersFormat.Value.NegativeSign ||
text == _numbersFormat.Value.PositiveSign ||
text == _numbersFormat.Value.NegativeSign + _numbersFormat.Value.NumberDecimalSeparator ||
text == _numbersFormat.Value.PositiveSign + _numbersFormat.Value.NumberDecimalSeparator)
return true;
// Now, lets check, whether text is a valid double
bool isValidDouble = StringEx.IsDouble(text);
// If text is a valid double - we're done
if (isValidDouble)
return true;
// Text could be invalid, but we still could accept such input.
// For example, we should accepted "1.", because after that user will type 1.12
// But we should not accept "..1"
int separatorCount = CountOccurances(text, _numbersFormat.Value.NumberDecimalSeparator);
// If text is not double and we don't have separator in this text
// or if we have more than one separator in this text, than text is invalid
if (separatorCount != 1)
return false;
// Lets remove first separator from our input text
string textWithoutNumbersSeparator = RemoveFirstOccurrance(text, _numbersFormat.Value.NumberDecimalSeparator);
// Second corner case:
// '.' is also valid text, because .1 is a valid double value and user may try to type this value
if (textWithoutNumbersSeparator.IsNullOrEmpty())
return true;
// Now, textWithoutNumbersSeparator should be valid if text contains only one
// numberic separator
bool isModifiedTextValid = StringEx.IsDouble(textWithoutNumbersSeparator);
return isModifiedTextValid;
}
/// <summary>
/// Returns number of occurances of value in text
/// </summary>
private static int CountOccurances(string text, string value)
{
string[] subStrings = text.Split(new[] { value }, StringSplitOptions.None);
return subStrings.Length - 1;
}
/// <summary>
/// Removes first occurance of valud from text.
/// </summary>
private static string RemoveFirstOccurrance(string text, string value)
{
if (string.IsNullOrEmpty(text))
return String.Empty;
if (string.IsNullOrEmpty(value))
return text;
int idx = text.IndexOf(value, StringComparison.InvariantCulture);
if (idx == -1)
return text;
return text.Remove(idx, value.Length);
}
}
}