Blazor client WASM form validation in component not working

Question

I am having trouble getting form validation to work properly in a Blazor WASM client application.

When an InputText element is encapsulated in a Blazor component, the InputText no longer performs validation.

When using a model like

public class Customer {
    [Required]
    [StringLength(100)]
    public string customerName {get; set;} = "";
}

in the form of

<EditForm Model=@customer>

<DataAnnotationsValidator />
<ValidationSummary />

<div class="form-row">

    <div class="form-group mb-0 col-sm-12">

        <div class="input-group input-group-sm mb-1 mt-1">
            <div class="input-group-prepend">
                <span class="input-group-text" style="width:6em;">Firma</span>
            </div>
            <InputText type="text" class="form-control" @bind-Value=customer.customerName />
        </div>

    </div>
</EditForm>

the validation works fine!

But when creating a modular Blazor component

@page "/inputGroup"

    <div class="input-group input-group-sm mb-1 mt-1">
        <div class="input-group-prepend">
            <span class="input-group-text" style="width:6em;">@label</span>
        </div>
        <InputText type=@type class="form-control" @bind-Value=@data @oninput=@onChange />
    </div>

@code {

    [Parameter]
    public string label {get; set;} = "Label:";

    [Parameter]
    public string type {get; set;} = "text";

    [Parameter]
    public string data {get; set;} = "";

    [Parameter]
    public EventCallback<string> dataChanged {get; set;}

    private Task onChange(ChangeEventArgs e) {

        data = (string)e.Value;
        return dataChanged.InvokeAsync(data);
    }
}

and then using it in this form

...
<div class="form-row">
    <div class="form-group mb-0 col-sm-12">
        <InputGroup label="Firma:" @bind-data=customer.customerName />
    </div>
</div>
...

the validation does not work!?

Could you update your pasted code to show where the EditForm is? Also, why does your embeddedable component have a @page directive? Do you intend to allow the user to navigate to /inputGroup? — Peter Morris
– Peter Morris, Commented Jun 11, 2020 at 10:58

thalacker · Accepted Answer · 2021-02-23 00:50:08Z

0

You could do something like this where you subclass InputText

InputTextGroup.razor

@inherits Microsoft.AspNetCore.Components.Forms.InputText

<div class="mt-1">
       <input type="text" id="@Id"
           @attributes="@AdditionalAttributes" @bind="@CurrentValueAsString"
           class="@CssClass myOtherCssClasses" />
</div>

@if (ValidationFor != null)
{
    <div class="myValidationClass">
        <ValidationMessage For="ValidationFor" />
    </div>
}

And InputTextGroup.razor.cs

public partial class InputTextGroup
{
    [Parameter] public string Id { get; set; } = HeadlessUI.HtmlElement.GenerateId();
    [Parameter] public string? Label { get; set; }
    [Parameter] public Expression<Func<string>>? ValidationFor { get; set; }
}

I took inspiration from this SO answer and this Microsoft docs

answered Feb 23, 2021 at 0:50

thalacker

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