Validation

Validation component is used to provide simple form validation for Blazorise input components. The basic structure for validation component is:

• <Validations> optional container for manual validation
  • <Validation> input container
    • <Feedback> messages placeholder
      • <ValidationSuccess> success message
      • <ValidationError> error message
      • <ValidationNone> message when nothing has happened
  • ValidationSummary lists all error messages

Notice: Starting from v0.9 it is advised to also surround Field components with Validation tags. This will ensure that validation will work in all scenarios!

Basic validation

For the most part you will need to use just the <Validation> component along with <ValidationSuccess> and <ValidationError>. By default every validation will run automatically when input value changes. You must set the Validator event handler where you can define the validation rules and return the validation result.}

Example

Here you can see the basic example for automatic validation and a custom function for checking the email.

<Validation Validator="@ValidateEmail">
    <TextEdit Placeholder="Enter email">
        <Feedback>
            <ValidationNone>Please enter the email.</ValidationNone>
            <ValidationSuccess>Email is good.</ValidationSuccess>
            <ValidationError>Enter valid email!</ValidationError>
        </Feedback>
    </TextEdit>
</Validation>
@code{
    void ValidateEmail( ValidatorEventArgs e )
    {
        var email = Convert.ToString( e.Value );

        e.Status = string.IsNullOrEmpty( email ) ? ValidationStatus.None :
            email.Contains( "@" ) ? ValidationStatus.Success : ValidationStatus.Error;
    }
}

The same structure is for all Edit components(check, radio, select, etc). Note that for some components there are some special rules when defining the validation structure. For example for Check you must use ChildContent tag along with the <Feedback> tag. This is a limitation in Blazor, hopefully it will be fixed in the future.

<Validation Validator="@ValidateCheck">
    <Check TValue="bool">
        <ChildContent>
            Check me out
        </ChildContent>
        <Feedback>
            <ValidationError>You must check me out!</ValidationError>
        </Feedback>
    </Check>
</Validation>

Async Validation

In case you need to run validation using the external source or rest API, we also support async validation. The process is similar to regular validator. You just need to define awaitable handler using the AsyncValidator parameter.

Example

<Validation AsyncValidator="@ValidateNameAsync">
    <TextEdit Placeholder="Enter name">
        <Feedback>
            <ValidationError>Enter valid name!</ValidationError>
        </Feedback>
    </TextEdit>
</Validation>
@code{
    async Task ValidateNameAsync( ValidatorEventArgs e, CancellationToken cancellationToken )
    {
        cancellationToken.ThrowIfCancellationRequested();

        // some long running task or call to the rest API
        await Task.Delay( random.Next( 600 ) );

        e.Status = string.IsNullOrEmpty( Convert.ToString( e.Value ) )
            ? ValidationStatus.Error
            : ValidationStatus.Success;
    }
}

Manual validation

Sometimes you don’t want to do validation on every input change. In that case you use <Validations> component to group multiple validations and then run the validation manually.

Example

In this example you can see how the <Validations> component is used to enclose multiple validation components and the Mode attribute is set to Manual. Validation is executed only when clicked on submit button.

<Validations @ref="validations" Mode="ValidationMode.Manual">
    <Validation Validator="@ValidateEmail">
        ...
    </Validation>
    <Validation Validator="@ValidatePassword">
        ...
    </Validation>
    <Button Color="Color.Primary" Clicked="@Submit">Submit</Button>
</Validations>
@code{
    Validations validations;

    void Submit()
    {
        validations.ValidateAll();
    }
}

Pattern validation

If you want to validate input by using regular expression instead of Validator handlers you can use Pattern attribute. Components that supports pattern attribute are TextEdit, NumericEdit and DateEdit.

Example

<Validation UsePattern="true">
    <TextEdit Pattern="[A-Za-z]{3}">
        <Feedback>
            <ValidationError>Pattern does not match!</ValidationError>
        </Feedback>
    </TextEdit>
</Validation>

Data Annotations

To use data annotations with Blazorise you must combine both Validation and the Validations components. The Validations component will act as a group for a fields used inside of Validation component. To make it all work you must meet two requirements:

1. Validations component must contain reference to the validated POCO through the Model attribute.
2. Input component must bind to the model field through the @bind-{Value}(i.e. @bind-Text)

After those two requirements are met the Blazorise will have enough information to know how to use data annotations.

Note: By default, Blazor will have enough information about the validating field when you use the two-way binding, eg. @bind-Text. In case you do the manual two-way binding with Text and TextChanged parameters you will also need to define a third parameter TextExpression that will tell Blazor everything about the validating field. To use TextExpression you need to define it as follows TextExpression="@(() => user.Name)"

Example

<Validations Mode="ValidationMode.Auto" Model="@user">
    <Validation>
        <Field Horizontal="true">
            <FieldLabel ColumnSize="ColumnSize.Is2">Full Name</FieldLabel>
            <FieldBody ColumnSize="ColumnSize.Is10">
                <TextEdit Placeholder="First and last name" @bind-Text="@user.Name">
                    <Feedback>
                        <ValidationError />
                    </Feedback>
                </TextEdit>
            </FieldBody>
        </Field>
    </Validation>
    <Validation>
        <Field Horizontal="true">
            <FieldLabel ColumnSize="ColumnSize.Is2">Email</FieldLabel>
            <FieldBody ColumnSize="ColumnSize.Is10">
                <TextEdit Placeholder="Enter email" @bind-Text="@user.Email">
                    <Feedback>
                        <ValidationError />
                    </Feedback>
                </TextEdit>
            </FieldBody>
        </Field>
    </Validation>
    <Validation>
        <Field Horizontal="true">
            <FieldLabel ColumnSize="ColumnSize.Is2">Password</FieldLabel>
            <FieldBody ColumnSize="ColumnSize.Is10">
                <TextEdit Role="TextRole.Password" Placeholder="Password" @bind-Text="@user.Password">
                    <Feedback>
                        <ValidationError />
                    </Feedback>
                </TextEdit>
            </FieldBody>
        </Field>
    </Validation>
    <Validation>
        <Field Horizontal="true">
            <FieldLabel ColumnSize="ColumnSize.Is2">Re Password</FieldLabel>
            <FieldBody ColumnSize="ColumnSize.Is10">
                <TextEdit Role="TextRole.Password" Placeholder="Retype password" @bind-Text="@user.ConfirmPassword">
                    <Feedback>
                        <ValidationError />
                    </Feedback>
                </TextEdit>
            </FieldBody>
        </Field>
    </Validation>
</Validations>

Model

public class User
{
    [Required]
    [StringLength( 10, ErrorMessage = "Name is too long." )]
    public string Name { get; set; }

    [Required]
    [EmailAddress( ErrorMessage = "Invalid email." )]
    public string Email { get; set; }

    [Required( ErrorMessage = "Password is required" )]
    [StringLength( 8, ErrorMessage = "Must be between 5 and 8 characters", MinimumLength = 5 )]
    [DataType( DataType.Password )]
    public string Password { get; set; }

    [Required( ErrorMessage = "Confirm Password is required" )]
    [StringLength( 8, ErrorMessage = "Must be between 5 and 8 characters", MinimumLength = 5 )]
    [DataType( DataType.Password )]
    [Compare( "Password" )]
    public string ConfirmPassword { get; set; }

    [Required]
    public string Title { get; set; }

    [Range( typeof( bool ), "true", "true", ErrorMessage = "You gotta tick the box!" )]
    public bool TermsAndConditions { get; set; }
}

Note: For a full source code you can look at the validation page inside of a demo application.

Localization

If you want to localize your validation messages, we got you covered. Blazorise will provide you with an API and all the required information needed for you to make localization. This is done through the MessageLocalizer API. But before you use it we need to break it down a little so you can understand it better how it works.

A MessageLocalizer is fairly straight forward. It accepts two parameters and returns a string. It’s signature is as following string Localize(string message, IEnumerable<string> arguments).

Where:

• format raw validation message
• arguments list of arguments or values for populating the message

So now that you know what the API consist of, we need to talk what is the content of the API. And the most important is the message parameter. Each message value will be represented as a raw message in the form before the actual message was formatted.

For example if you have a [Required] attribute set on your model field, this message will be "The {0} field is required.". And the arguments will contain all the values needed to populate the placeholders inside of the message.

Example

For the basic example we’re going to use MessageLocalizer directly on a Validation component.

<Validation MessageLocalizer="@Localize">

[Inject] IStringLocalizer<YourResource> L;

string Localize( string message, IEnumerable<string> arguments )
{
    // You should probably do null checks here!
    return string.Format( L[message], arguments.ToArray() );
}

Note: We assumed you will get all your localization through the IStringLocalizer. If you’re using something else you will need to modify code according to your requirements.

Global Options

Setting the MessageLocalizer on each Validation is a good for approach if you want to control every part of your application. But a more practical way is to define it globally. If you remember from the Start Guide, we already have AddBlazorise defined in our application startup so we just need to modify it a little.

services
    .AddBlazorise( options =>
    {
        // other settings

        options.ValidationMessageLocalizer = ( message, arguments ) =>
        {
            var stringLocalizer = options.Services.GetService<IStringLocalizer<YourResource>>();

            return stringLocalizer != null && arguments?.Count() > 0
                ? string.Format( stringLocalizer[message], arguments.ToArray() )
                : message;
        };
    } )

Validation summary

Sometimes you don’t want to show error messages under each field. In those situations you can use ValidationSummary component. Once placed inside of Validations it will show all error messages as a bullet list.

<Validations @ref="annotationsValidations" Mode="ValidationMode.Manual" Model="@manualUser">
    <ValidationSummary Label="Following error occurs..." />

    // other validation fields
</Validations>

Auto Validation

By default form is auto-validated on page load. In case you want to disable it and validate only when user starts entering fields, now you can. Just set ValidateOnLoad to false.

<Validations Mode="ValidationMode.Auto" ValidateOnLoad="true">
    ...
</Validations>

Validation rules

In Blazorise you can use some of the predefined validation rules. eg

<Validation Validator="@ValidationRule.IsNotEmpty">

List of the currently available validators.

Validator	Description
IsEmpty	Check if the string is null or empty.
IsNotEmpty	Check if the string is not null or empty.
IsEmail	Check if the string is an email.
IsAlpha	Check if the string contains only letters (a-zA-Z).
IsAlphanumeric	Check if the string contains only letters and numbers.
IsAlphanumericWithUnderscore	Check if the string contains only letters, numbers and underscore.
IsUppercase	Check if the string is uppercase.
IsLowercase	Check if the string is lowercase.

Attributes

Validations

Name	Type	Default	Description
Mode	ValidationMode	Auto	Defines the validation mode for validations inside of this container.
EditContext	EditContext	null	Supplies the edit context explicitly. If using this parameter, do not also supply Model, since the model value will be taken from the Model property.
Model	object	null	Specifies the top-level model object for the form. An edit context will be constructed for this model.
MissingFieldsErrorMessage	string		Message that will be displayed if any of the validations does not have defined error message.
ValidatedAll	EventCallback		Event is fired only after all of the validation are successful.
StatusChanged	EventCallback		Event is fired whenever there is a change in validation status.
ValidateOnLoad	bool		Run validation only when user starts entering values.

Validation

Name	Type	Default	Description
Status	ValidationStatus	None	Gets or sets the current validation status.
StatusChanged	EventCallback		Event is fired whenever there is a change in validation status.
Validator	action		Validates the input value after it has being changed.
UsePattern	boolean	false	Forces validation to use regex pattern matching instead of default validator handler.
MessageLocalizer	Func<ValidationMessageLocalizerEventArgs, IEnumerable<string>>	null	Custom handler used to override error messages in case the localization is needed.