.NET MAUI DataForm Validation

.NET MAUI DataForm provides built-in validation, which gives you full control over the data collected through the control.

The next sections list all DataForm members related to validation.

Validation modes

The selected mode is applied through ValidationMode(of typeTelerik.Maui.Controls.DataFormValidationMode) property of the DataForm control. You could choose between three validation modes:

• Explicit—The changes are validated explicitly by invoking the ValidateCommand or calling the ValidateChanges method of the DataForm.
• LostFocus—The changes are validated after the editor loses focus.
• PropertyChanged—The changes in the editor are validated immediately on each property change (when the property value changes).

When ValidationMode is set to LostFocus, you have to set CommitMode to LostFocus or Explicit.

The ValidationMode can be applied globally to the RadDataForm

<telerik:RadDataForm x:Name="dataForm"
                     ValidationMode="LostFocus"/>

Validation properties

• HasValidationErrors(bool)—Gets a value indicating whether there are validation errors.

Events

DataForm exposes the following events for validation:

• ValidationCompleted—Raised when the DataForm validation completes. The ValidationCompleted event handler receives two parameters:

  • sender argument which is of type object, but can be cast to the RadDataForm type.
  • DataFormObjectValidationCompletedEventArgs which probvides additional information for the validated DataObject, the ValidationErros(IReadOnlyList of DataFormValidationError) and whether there are validation errors HasValidationErrors(bool).

• EditorValidationCompleted—Raised when the validation of an editor has completed. The EditorValidationCompleted event handler receives two parameters:

  • sender argument which is of type object, but can be cast to the RadDataForm type.
  • DataFormEditorValidationCompletedEventArgs which probvides additional information for the validated PropertyName, the original value ff the validated property PropertyValue(object) in the model and the modified value of the validated property in the editor - EditorValue(object).

Manual Validation with Methods

DataForm exposes a ValidateChanges method with two overloads:

• ValidateChanges()—Executes the validation logic associated with the DataForm control. This method is mostly useful when the ValidationMode is set to Explicit. The method returns true if the validation passes, otherwise false.

this.dataForm.ValidateChanges();

• ValidateChanges(string propertyName)—Validates the pending changes in the editor for the specified property. This method is mostly useful when the DataForm ValidationMode property is set to Explicit. True if the validation passes, false otherwise.

this.dataForm.ValidateChanges(propertyName);

Commands

• ValidateCommand(ICommand)—Gets a command to execute the validation logic of the RadDataForm. This command is mostly useful when the DataForm ValidationMode property is set to Explicit.

Validation summary - styling and customization

The ValidationSummaryMessage displays all validation messages for the editors. You can visualize/hide the validation summary message by setting the IsValidationSummaryVisible(bool) property to True/False.

You can use the following properties for validation styling and customization:

• ValidationSummaryImageSource(ImageSource)—Specifies the ImageSource of the image displayed in the validation summary.
• ValidationSummaryImageStyle(Style)—Specifies the style applied to the image of the validationsummary. The target type of this style is the .NET MAUI Image control.
• ValidationSummaryStyle(Style)—Specifies the style applied to the validation summary. The target type of this style is the Telerik.Maui.Controls.DataFormValidationSummaryView.
  
• ValidationSummaryLabelStyle(Style)—Specifies the style applied to the labels of the validation summary. The target type of this style is the .NET MAUI Label control.

Error message - styling and customization

You can use the following properties for error message styling and customization:

• ErrorImageSource(ImageSource)—Specifies the ImageSource of the image displayed in the error message.
• ErrorImageStyle(Style)—Specifies the style applied to the image of the error message. The target type of this style is the .NET MAUI Image control.
• ErrorLabelStyle(Style)—Specifies the style applied to the labels of the error message. The target type of this style is the .NET MAUI Label control.

See Also

• Editors
• Grouping
• Headers
• Layouts
• Commit Data
• Commands