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POHow to validate data in WPF and set default value?
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  1. POHow to validate data in WPF and set default value?
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    copied!<p>I'm trying to perform a validation property. We have a nullable property called:</p> <pre><code> public int? Number { get { return _number; } set { if (_number != value) { _number = value; RaisePropertyChanged("Number"); } } } </code></pre> <p>And this property is bound to a textbox. I only want to validate this two escenarios:</p> <ul> <li>Imagine that the user left the textbox empty (textbox.text=""), so Number property must receive null value (instead "" ).</li> <li>And if the user inputs "2b", Number property must have a null value (because is an error), but the textbox must still say "2b".</li> </ul> <p>I guess IDataNotifyError and ValidationRules is not working for this. How can I resolve these situations?</p> <p>EDIT: I'm using also a ValidationRule to show a custom message when the user inputs an incorrect format. But when this happens, does not fire the property to null. And if a put true in that error, it fired, but does not show any error message.</p> <pre><code> &lt;TextBox.Text&gt; &lt;Binding Path="Number" UpdateSourceTrigger="PropertyChanged" ValidatesOnDataErrors="True" ValidatesOnExceptions="True" NotifyOnValidationError="True" Converter="{x:Static c:IntConverter.Default}" &gt; &lt;Binding.ValidationRules&gt; &lt;r:NumericValidation /&gt; &lt;/Binding.ValidationRules&gt; &lt;/Binding&gt; &lt;/TextBox.Text&gt; </code></pre> <p>The validation rule</p> <pre><code>public class NumericValidation : ValidationRule { public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo) { int? response; bool noIllegalChars = TryParseStruct&lt;int&gt;(value.ToString(), out response); if (noIllegalChars == false) { return new ValidationResult(false, "Input is not in a correct format."); } else { return new ValidationResult(true, null); } } ... } </code></pre>
 

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