Canceling TextBox input on validation error in WPF -


I am trying to understand how to cancel user input in a verification error textbox Happens in. If the user tries to enter an invalid character then I would like to stop it from being added to textbox .

How do I accept text box invalid characters? TextBox.TextChanged Event

My TextBox looks like: 

  & lt; Textbox validation. Error = "On-Thomtextbox Formatting Error" & gt; & Lt; TextBox.Text & gt; & Lt; Binding Path = Indicate "Value" authenticationArray = "true" update source source = "property changed" & gt; & Lt; Binding.ValidationRules & gt; & Lt; Local: Some ValidationRule / & gt; & Lt; /Binding.ValidationRules> & Lt; / Binding & gt; & Lt; /TextBox.Text> & Lt; / Text box & gt;

My custom verification rule looks like: 

  Public class SomeValidationRule: Validation rules {Valid for public override validation (Object Value, CultureInfo cultureInfo) {string Hex_string = value like rope; Match invalid_church = regsx Match (hex_string, "[^ 0- 9a-fa-f]"); Bool is_valid = (invalid_chars.Success == incorrect); String error_context = null; If (is_valid == is incorrect) {error_context = "invalid character"; } New validation return return (is_valid, error_context); }}

I have an error handler ... can I do something with it? 

  Private ZeroOnSiteTextBox ValidationAir (Object Sender, ValidationAirEventErguesE) / Can I do anything here? }

Please answer the original if possible, instead of referencing the URL. I have read the possible solutions to event handlers, but I have not come to any person who discusses the possibility of doing all my beliefs in the validation rule .

After a lot of research, it seems that on the input of a textbox The only way to keep complete control is to have several incidents directly according to the WPF recipe according to C # 2008 (1 edition, p. 169):

Unfortunately, useful, high-level data binding feature There is no easy way to combine (currently) lower-level keyboard handling, which allows the user to enter invalid characters Issues would be necessary to prevent the typing.

Here I came to create a hexadecimal numerical TextBox only accepts AP, Air Force and 0-9 characters.

Some classes. Xml 

  & gt; Text Box X: Name = "Some Text Box" Lost Focus = "Text Box Lostfox" Preview Key = "Text Box Preview" Preview "PreviewInput =" Textbox Prevent Input "/>

SomeClass.xaml.cs 

  private string mInvalidCharPattern = "[^ 0-9a-fA-F]"; // SomeClass () {DataObject.AddPastingHandler (This.SomeTextBox, New DataObjectPastingEventHandler (TextboxPasting)) received from SomeClass UserControl in my case; } Private Zero TextBoxLostFocus (Object Sender, RoutedEventArgs E) {// You want to refresh the text box text here. If the user deletes the contents of the text box and clicks on it, you can restore the original value to //. } // Hold the space character, since this PreviewTextInput does not trigger the Private Zero Text Box Preview (Object Sender, Key EventErgus E) {if (E.K. == Key Space) {e.Handled = true; }} // Most validity here Private Zero text box prevoct input (object sender, text composite events E) {if (valid text input (E. text) == incorrect) {e.Handled = true; }} // Avoid pasting invalid characters Private Zero Text Box (Object Sender, DataObjectPastingEventArgs E) {string lPastingText = e.DataObject.GetData (DataFormats.Text) as string; If (valid text (lPastingText) == incorrect) {E. Console comand (); }} // Verify in a different function, which can be valid for private hair, test input (string one text input) {if (aTextInput == faucet) {return false; } Match lInvalidMatch = Regex.Match (aTextInput, this.mInvalidCharPattern); Return (lInvalidMatch.Success == incorrect); }

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