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WPF Validation: How to Validate the Whole Form on the Button Click

The validation is only successful if the value is not null and empty. Let’s check out another validation rule which forces a developer too type a numeric input into the TextBox. This custom user control only consist of only the basic features and can easily be extended to add more rich features. Let’s check out the details of how to implement the validation rules. WPF validation can be set up to highlight/tooltip-explain bad fields when they lose focus; that way the user’s complete input is available.

  • In a case where there is a dependency between fields and if changing the value forces another field to update, again notify the user about the change to a previous field they filled out.
  • You can call the BaseEdit.ClearError method to reset invalid values.
  • After validation, when the value of the DoubleTextBox is greater than the MaxValue or less than the MinValue, the value will be automatically set to MaxValue or MinValue.
  • It basically enables you to move the validation logic from the controller to the model which effectively makes it easier to write unit tests for the the controller actions.

In the above XAML code you can see that I have used the explicit Text binding. The reason for that is that I can set the validation rules collection with the instance of the RegexValidationRule class. The code above validates the user input against the null and empty values.

Automatic Validation Using Masks

A good example would be a forward reference to a resource defined later on in the XAML. Another example is a resource that will not even exist until runtime. It will update the target if the source resource dictionary is changed. @JonW It is just a general link to Microsoft Validation. «Any good reads/sources on WPF validation?» In the first comment I stated Validation uses border and tool tips.

IDataErrorInfo is an interface used to validate data changes and notify the view if there is any error in the data. This interface has two members, a string indicating what is wrong in the object, and a string indicating what is wrong in the specific property of that object. The following steps explain how to implement the form data validation using IDataErrorInfo. As, you can see in the XAML code above the custom RequiredTextbox contains two validation rules. Both the rules will be triggered on the LostFocus event. Below you can see the screenshot of the validation rules in action which you tab of the TextBox control without entering any value.

MaxValueOnExceedMinDigit property will be enabled only when the MaxValidation is set to OnKeyPress. This section explains how to validate or restrict the DoubleTextBox control value. I totally agree with Martin, you should write a book (if you haven’t done so already).

In such cases, the height of the webpage is just extended to accommodate the additional text, if needed. OnKeyPress — When setting the MaxValidation or MinValidation to OnKeyPress, the value in the DoubleTextBox will be validated shortly after pressing a key. So, it is not possible to provide any invalid input at all and the value does not exceed the maximum and minimum limits.

wpf textbox validation

The helper’s IDataErrorInfoHelper.GetErrorText method returns error text for each data item’s field. If an editor’s BaseEdit.CausesValidation property is set to true, the BaseEdit.Validate event is raised for the editor. A StaticResource will be resolved and assigned to the property during the loading of the XAML which occurs before the application is actually run. It will only be assigned once and any changes to resource dictionary ignored.

WPF Validation: How to Validate the Whole Form on the Button Click

Visually change the styling of the field and not displaying any helpful text. Main issue here is with accessibility as some people may not even notice a color change. Automatically changing a valueYou should be notifying a user that a potential issue / mistake was made and suggest the right answer if you are able to do so. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. I agree to the creation of a Syncfusion account in my name and to be contacted regarding this message. When value of MinimumNumberDecimalDigits, MaximumNumberDecimalDigits and NumberDecimalDigits properties are specified, NumberDecimalDigits property takes high precedence and updates the text of DoubleTextBox property.

You can choose when to validate the maximum and minimum limits while changing the values by using the MinValidation and MaxValidation properties. The RadCardView control provides few events that are raised whenever the data is changed using the UI – CardValidating, CardDataFieldValidating and CardDataFieldValidated. The POCO View Models can automatically implement the IDataErrorInfo https://cryptonews.wiki/ interface based on the specified Data Annotation Attributes attributes. Refer to the Automatic IDataErrorInfo Implementation section for more information. The code sample below illustrates how to customize the error with a SetError method call. To show error information as a tooltip of the editor, bind the tooltip to ‘Validation.Errors’ as demonstrated in the following code.

wpf textbox validation

We need to inform the user by providing an error message on the view. The GetErrors method of the interface returns an IEnumerable that contains validation errors for the specified property or for the entire entity. You should always raise the ErrorsChanged event whenever the collection returned by the GetErrors method changes. Correspondingly, an underlying data value in the view model is automatically updated when the user modifies the bound value in the view. A common requirement for any user interface application that accepts user input is to validate the entered information to ensure that it has the expected format and type for the back-end to be able to accept and persist it. It also contains an example that shows how you can validate data using data annotations.

A Common Example IDataErrorInfo

Users are most likely to provide short pieces of the info. The Value of the DoubleTextBox can be restricted within the maximum and minimum limits. Once the value has reached the maximum or minimum value , the value does not exceed the limit. We can change the maximum and minimum limits by using the MinValue property and MaxValue property. If the binding has a converter, its ConvertBack method gets called. Implement the IDataErrorInfo interface based on your data object.

wpf textbox validation

The IDataErrorInfo interface is the standard mechanism for data validation in WPF. You can use this interface to implement validation rules for each property or the entire object. INotifyDataError is also used to validate the data changes and notify if there is any error in the data. This interface notifies the view by raising the ‘ErrorChanged’ event. This interface can also show multiple error information for a single property. The following steps explain how to implement the form data validation using INotifyDataErrorInfo.

«Do we change the values from incorrect ones to a default correct one?» All you have done is say ‘do what microsoft do’ but then not actually explained what that is and why it is appropriate. (Adding a link and expecting everyone to click through to it and find the answer themselves doesn’t really qualify as an answer in its own right, it’s just a link). I’ve seen cases where «Submit» button is disabled until all fields pass validation. It may sound like a good idea at first, but you don’t want your user to keep guessing why the button does not work and what they may be missing. It’s ok to disable the button after initial submit and while the errors are shown (assumption that field validation happens on «keyup» so as soon as the last field passes validation – the button reactivates instantly).


Value will changed to 100 when MaxValueOnExceedMaxDigit is true. When MaxValueOnExceedMaxDigit is false, 20 will be retained and last entered 0 will be ignored. Note that the Validation.ErrorTemplate will be displayed on the adorner layer. Elements in the adorner layer are rendered on top of the rest of the visual elements and they will not be considered when 5 Step Proven Process How to Outsource Software Development the layout system is measuring and arranging the controls on the adorned element layer. The adorned element in this case is the TextBox control itself and you include an AdornedElementPlaceholder in the control template where you want to leave space for it. The template above will cause the error message to be displayed in a TextBlock below the TextBox.

In our sample project, we have four TextBox elements. Each of them presents a different style of presenting the occurred error to the user. When an error occurs on the data binding the attached property Validation.HasError property is set to true on the target element of the data binding process (in our case it’s TextBox element).

In this post, I will show how you can present user input validation errors to the user. By default, WPF shows a red border around the TextBox when the entered value is invalid. But in this case, our user has no idea what is wrong with entered data.

And a view model which binds to this UI contains two properties. Windows Presentation Foundation allows the developers to create attractive Windows applications by provided styles, graphics etc. One the major pain points of using WPF is that it lacks the validation framework. Microsoft WPF team did not put much effort in creating a reliable validation system.

Do we change the values from incorrect ones to a default correct one? Our mission is to validate the TextBox on lost focus event hence, we are going to implement the TextBox lost focus event. MinValueOnExceedMinDigit – When you give input less than specified minimum limit, MinValueOnExceedMinDigit property will decide either it should retain the old value or reset to minimum limit that is specified. For example, if MinValue is set to 200 and the Value is 205 and you are trying change the value to 20.

An editor can block focus transition to other controls until a valid value is entered (see BaseEdit.InvalidValueBehavior). You can call the BaseEdit.DoValidate method to validate user input at any moment. Exceptions are one of the only ways to catch some types of input invalidations and are explicitly used it MS docs. Also this is UI, single input validation, not entire objects. One of the advantage of this validation is that is discards the value of the property before being set to the property variable and don’t store the value in the member variable of class. In this article I will discuss all the ways in which we can validate data in the WPF application.

Note that the TextBlock will appear on top of any elements that are located right below the TextBox as adorners are always visually on top. DevExpress Data Editors validate user input when input masks are enabled. Masks let you specify the pattern for input values and users cannot enter text which is not permitted.