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Set the Editor in invalid state when validation does not pass


Product Editor for Blazor


I would like to set the Editor in invalid state when validation does not pass by adding a red border around the component.

The goal (result) from the solution below

the editor in invalid state


The Editor is a composite component and as such, currently, does not support the k-invalid class. In order to add a red border when the validation set for its value does not pass you can make a custom CSS class that mimics k-invalid and add it to the Class parameter based on a bool expression.

You can utilize the capabilities and information provided by the EditContext to determine if the validation did not pass for the exact field bound to the Editor and render anew the component to apply the custom CSS class. A step by step explanation and an example of those concepts can be found below.

Step by step explanation:

  1. Create a custom CSS class that mimics the k-invalid.
  2. Pass an EditContext to the <EditForm>.
  3. Instantiate a FieldIdentifier and in its constructor pass the data model and the field bound to the Editor.
  4. Use a getter-only property to check if there are any validation messages for that FieldIdentifier.
  5. In the handler for the OnValidationStateChanged event call a StateHasChanged() to render the component anew.
  6. Use the Class parameter to pass the custom CSS class.

Set the Editor in invalid state when validation does not pass

@*This is the custom class that mimics k-invalid*@
    .myCustomInvalidState {
        border-color: #dc3545;

@using System.ComponentModel.DataAnnotations

<EditForm EditContext="@MyEditContext" OnValidSubmit="@HandleValidSubmit">
    <DataAnnotationsValidator />
    <ValidationSummary />

    <TelerikEditor @bind-Value="@theProduct.Description" Class="@(IsEditorInvalidSubmit ? "myCustomInvalidState" : "")">

    <TelerikButton ButtonType="@ButtonType.Submit">Submit</TelerikButton>

@code {
    protected EditContext MyEditContext { get; set; }

    public FieldIdentifier EditorFieldIdentifier { get; set; } // instantiating a FieldIdentifier for the Editor,
                                                               // see the OnInitialize on how to pass the model and the field

    //checking for validation messages for the editor
    public bool IsEditorInvalidSubmit => MyEditContext.GetValidationMessages(EditorFieldIdentifier).Any();

    //calling StateHasChanged to render the component again
    private void HandleValidationStateChanged(object o, ValidationStateChangedEventArgs args) => StateHasChanged();

    protected override void OnInitialized()
        MyEditContext = new EditContext(theProduct);
        EditorFieldIdentifier = new FieldIdentifier(theProduct, nameof(theProduct.Description));
        MyEditContext.OnValidationStateChanged += HandleValidationStateChanged;

    public class Product
        [Required(ErrorMessage = "Description is required")]
        [MaxLength(100, ErrorMessage = "The max allowed length of the content is 100 symbols")]
        [MinLength(20, ErrorMessage = "The min allowed length of the content is 20 symbols")]
        public string Description { get; set; }

    Product theProduct = new Product();

    void HandleValidSubmit()
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