title	author	description	monikerRange	ms.author	ms.custom	ms.date	uid
ASP.NET Core Blazor forms overview	guardrex	Learn how to use forms in Blazor.	>= aspnetcore-3.1	riande	mvc	02/09/2024	blazor/forms/index

ASP.NET Core Blazor forms overview

[!INCLUDE]

This article explains how to use forms in Blazor.

Input components and forms

The Blazor framework supports forms and provides built-in input components:

:::moniker range=">= aspnetcore-8.0"

Bound to an object or model that can use data annotations
- HTML forms with the <form> element
- xref:Microsoft.AspNetCore.Components.Forms.EditForm components
Built-in input components

:::moniker-end

:::moniker range="< aspnetcore-8.0"

An xref:Microsoft.AspNetCore.Components.Forms.EditForm component bound to an object or model that can use data annotations
Built-in input components

:::moniker-end

The xref:Microsoft.AspNetCore.Components.Forms?displayProperty=fullName namespace provides:

Classes for managing form elements, state, and validation.
Access to built-in :::no-loc text="Input*"::: components.

A project created from the Blazor project template includes the namespace by default in the app's _Imports.razor file, which makes the namespace available to the app's Razor components.

:::moniker range=">= aspnetcore-8.0"

Standard HTML forms are supported. Create a form using the normal HTML <form> tag and specify an @onsubmit handler for handling the submitted form request.

StarshipPlainForm.razor:

:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/Pages/StarshipPlainForm.razor":::

In the preceding StarshipPlainForm component:

The form is rendered where the <form> element appears. The form is named with the @formname directive attribute, which uniquely identifies the form to the Blazor framework.
The model is created in the component's @code block and held in a public property (Model). The [SupplyParameterFromForm] attribute indicates that the value of the associated property should be supplied from the form data. Data in the request that matches the property's name is bound to the property.
The xref:Microsoft.AspNetCore.Components.Forms.InputText component is an input component for editing string values. The @bind-Value directive attribute binds the Model.Id model property to the xref:Microsoft.AspNetCore.Components.Forms.InputText component's xref:Microsoft.AspNetCore.Components.Forms.InputBase%601.Value%2A property.
The Submit method is registered as a handler for the @onsubmit callback. The handler is called when the form is submitted by the user.

Important

Always use the @formname directive attribute with a unique form name.

Blazor enhances page navigation and form handling by intercepting the request in order to apply the response to the existing DOM, preserving as much of the rendered form as possible. The enhancement avoids the need to fully load the page and provides a much smoother user experience, similar to a single-page app (SPA), although the component is rendered on the server. For more information, see xref:blazor/fundamentals/routing#enhanced-navigation-and-form-handling.

Streaming rendering is supported for plain HTML forms.

[!INCLUDE]

The preceding example includes antiforgery support by including an xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryToken component in the form. Antiforgery support is explained further in the Antiforgery support section of this article.

To submit a form based on another element's DOM events, for example oninput or onblur, use JavaScript to submit the form (submit (MDN documentation)).

Instead of using plain forms in Blazor apps, a form is typically defined with Blazor's built-in form support using the framework's xref:Microsoft.AspNetCore.Components.Forms.EditForm component. The following Razor component demonstrates typical elements, components, and Razor code to render a webform using an xref:Microsoft.AspNetCore.Components.Forms.EditForm component.

:::moniker-end

:::moniker range="< aspnetcore-8.0"

A form is defined using the Blazor framework's xref:Microsoft.AspNetCore.Components.Forms.EditForm component. The following Razor component demonstrates typical elements, components, and Razor code to render a webform using an xref:Microsoft.AspNetCore.Components.Forms.EditForm component.

:::moniker-end

Starship1.razor:

:::moniker range=">= aspnetcore-8.0"

:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/Pages/Starship1.razor":::

In the preceding Starship1 component:

The xref:Microsoft.AspNetCore.Components.Forms.EditForm component is rendered where the <EditForm> element appears. The form is named with the @formname directive attribute, which uniquely identifies the form to the Blazor framework.
The model is created in the component's @code block and held in a public property (Model). The property is assigned to the xref:Microsoft.AspNetCore.Components.Forms.EditForm.Model?displayProperty=nameWithType parameter. The [SupplyParameterFromForm] attribute indicates that the value of the associated property should be supplied from the form data. Data in the request that matches the property's name is bound to the property.
The xref:Microsoft.AspNetCore.Components.Forms.InputText component is an input component for editing string values. The @bind-Value directive attribute binds the Model.Id model property to the xref:Microsoft.AspNetCore.Components.Forms.InputText component's xref:Microsoft.AspNetCore.Components.Forms.InputBase%601.Value%2A property.
The Submit method is registered as a handler for the xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnSubmit callback. The handler is called when the form is submitted by the user.

Important

Always use the @formname directive attribute with a unique form name.

Blazor enhances page navigation and form handling for xref:Microsoft.AspNetCore.Components.Forms.EditForm components. For more information, see xref:blazor/fundamentals/routing#enhanced-navigation-and-form-handling.

Streaming rendering is supported for xref:Microsoft.AspNetCore.Components.Forms.EditForm.

[!INCLUDE]

:::moniker-end

:::moniker range="< aspnetcore-8.0"

@page "/starship-1"
@inject ILogger<Starship1> Logger

<EditForm Model="Model" OnSubmit="Submit">
    <InputText @bind-Value="Model!.Id" />
    <button type="submit">Submit</button>
</EditForm>

@code {
    public Starship? Model { get; set; }

    protected override void OnInitialized() => Model ??= new();

    private void Submit()
    {
        Logger.LogInformation("Model.Id = {Id}", Model?.Id);
    }

    public class Starship
    {
        public string? Id { get; set; }
    }
}

In the preceding Starship1 component:

The xref:Microsoft.AspNetCore.Components.Forms.EditForm component is rendered where the <EditForm> element appears.
The model is created in the component's @code block and held in a private field (model). The field is assigned to the xref:Microsoft.AspNetCore.Components.Forms.EditForm.Model?displayProperty=nameWithType parameter.
The xref:Microsoft.AspNetCore.Components.Forms.InputText component is an input component for editing string values. The @bind-Value directive attribute binds the Model.Id model property to the xref:Microsoft.AspNetCore.Components.Forms.InputText component's xref:Microsoft.AspNetCore.Components.Forms.InputBase%601.Value%2A property†.
The Submit method is registered as a handler for the xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnSubmit callback. The handler is called when the form is submitted by the user.

:::moniker-end

†For more information on property binding, see xref:blazor/components/data-binding#binding-with-component-parameters.

In the next example, the preceding component is modified to create the form in the Starship2 component:

xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnSubmit is replaced with xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnValidSubmit, which processes assigned event handler if the form is valid when submitted by the user.
A xref:Microsoft.AspNetCore.Components.Forms.ValidationSummary component is added to display validation messages when the form is invalid on form submission.
The data annotations validator (xref:Microsoft.AspNetCore.Components.Forms.DataAnnotationsValidator component†) attaches validation support using data annotations:
- If the <input> form field is left blank when the Submit button is selected, an error appears in the validation summary (xref:Microsoft.AspNetCore.Components.Forms.ValidationSummary component‡) ("The Id field is required.") and Submit is not called.
- If the <input> form field contains more than ten characters when the Submit button is selected, an error appears in the validation summary ("Id is too long."). Submit is not called.
- If the <input> form field contains a valid value when the Submit button is selected, Submit is called.

†The xref:Microsoft.AspNetCore.Components.Forms.DataAnnotationsValidator component is covered in the Validator component section. ‡The xref:Microsoft.AspNetCore.Components.Forms.ValidationSummary component is covered in the Validation Summary and Validation Message components section.

Starship2.razor:

:::moniker range=">= aspnetcore-8.0"

:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/Pages/Starship2.razor":::

:::moniker-end

:::moniker range="< aspnetcore-8.0"

@page "/starship-2"
@using System.ComponentModel.DataAnnotations
@inject ILogger<Starship2> Logger

<EditForm Model="Model" OnValidSubmit="Submit">
    <DataAnnotationsValidator />
    <ValidationSummary />
    <InputText @bind-Value="Model!.Id" />
    <button type="submit">Submit</button>
</EditForm>

@code {
    public Starship? Model { get; set; }

    protected override void OnInitialized() => Model ??= new();

    private void Submit()
    {
        Logger.LogInformation("Id = {Id}", Model?.Id);
    }

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

:::moniker-end

Handle form submission

The xref:Microsoft.AspNetCore.Components.Forms.EditForm provides the following callbacks for handling form submission:

Use xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnValidSubmit to assign an event handler to run when a form with valid fields is submitted.
Use xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnInvalidSubmit to assign an event handler to run when a form with invalid fields is submitted.
Use xref:Microsoft.AspNetCore.Components.Forms.EditForm.OnSubmit to assign an event handler to run regardless of the form fields' validation status. The form is validated by calling xref:Microsoft.AspNetCore.Components.Forms.EditContext.Validate%2A?displayProperty=nameWithType in the event handler method. If xref:Microsoft.AspNetCore.Components.Forms.EditContext.Validate%2A returns true, the form is valid.

Clear a form or field

Reset a form by clearing its model back its default state, which can be performed inside or outside of an xref:Microsoft.AspNetCore.Components.Forms.EditForm's markup:

<button @onclick="ClearForm">Clear form</button>

...

private void ClearForm() => Model = new();

Alternatively, use an explicit Razor expression:

<button @onclick="@(() => Model = new())">Clear form</button>

Reset a field by clearing its model value back to its default state:

<button @onclick="ResetId">Reset Identifier</button>

...

private void ResetId() => Model!.Id = string.Empty;

Alternatively, use an explicit Razor expression:

<button @onclick="@(() => Model!.Id = string.Empty)">Reset Identifier</button>

There's no need to call xref:Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged%2A in the preceding examples because xref:Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged%2A is automatically called by the Blazor framework to rerender the component after an event handler is invoked. If an event handler isn't used to invoke the methods that clear a form or field, then developer code should call xref:Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged%2A to rerender the component.

:::moniker range=">= aspnetcore-8.0"

Antiforgery support

Antiforgery services are automatically added to Blazor apps when xref:Microsoft.Extensions.DependencyInjection.RazorComponentsServiceCollectionExtensions.AddRazorComponents%2A is called in the Program file.

The app uses Antiforgery Middleware by calling xref:Microsoft.AspNetCore.Builder.AntiforgeryApplicationBuilderExtensions.UseAntiforgery%2A in its request processing pipeline in the Program file. xref:Microsoft.AspNetCore.Builder.AntiforgeryApplicationBuilderExtensions.UseAntiforgery%2A is called after the call to xref:Microsoft.AspNetCore.Builder.EndpointRoutingApplicationBuilderExtensions.UseRouting%2A. If there are calls to xref:Microsoft.AspNetCore.Builder.EndpointRoutingApplicationBuilderExtensions.UseRouting%2A and xref:Microsoft.AspNetCore.Builder.EndpointRoutingApplicationBuilderExtensions.UseEndpoints%2A, the call to xref:Microsoft.AspNetCore.Builder.AntiforgeryApplicationBuilderExtensions.UseAntiforgery%2A must go between them. A call to xref:Microsoft.AspNetCore.Builder.AntiforgeryApplicationBuilderExtensions.UseAntiforgery%2A must be placed after calls to xref:Microsoft.AspNetCore.Builder.AuthAppBuilderExtensions.UseAuthentication%2A and xref:Microsoft.AspNetCore.Builder.AuthorizationAppBuilderExtensions.UseAuthorization%2A.

The xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryToken component renders an antiforgery token as a hidden field, and the [RequireAntiforgeryToken] attribute enables antiforgery protection. If an antiforgery check fails, a 400 - Bad Request response is thrown and the form isn't processed.

For forms based on xref:Microsoft.AspNetCore.Components.Forms.EditForm, the xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryToken component and [RequireAntiforgeryToken] attribute are automatically added to provide antiforgery protection by default.

For forms based on the HTML <form> element, manually add the xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryToken component to the form:

<form method="post" @onsubmit="Submit" @formname="starshipForm">
    <AntiforgeryToken />
    <input id="send" type="submit" value="Send" />
</form>

@if (submitted)
{
    <p>Form submitted!</p>
}

@code{
    private bool submitted = false;

    private void Submit() => submitted = true;
}

Warning

For forms based on either xref:Microsoft.AspNetCore.Components.Forms.EditForm or the HTML <form> element, antiforgery protection can be disabled by passing required: false to the [RequireAntiforgeryToken] attribute. The following example disables antiforgery and is not recommended for public apps:

@using Microsoft.AspNetCore.Antiforgery
@attribute [RequireAntiforgeryToken(required: false)]

For more information, see xref:blazor/security/index#antiforgery-support.

:::moniker-end

:::moniker range=">= aspnetcore-8.0"

Enhanced form handling

Enhance navigation for form POST requests with the xref:Microsoft.AspNetCore.Components.Forms.EditForm.Enhance%2A parameter for xref:Microsoft.AspNetCore.Components.Forms.EditForm forms or the data-enhance attribute for HTML forms (<form>):

<EditForm ... Enhance ...>
    ...
</EditForm>

<form ... data-enhance ...>
    ...
</form>

❌Unsupported: You can't set enhanced navigation on a form's ancestor element to enable enhanced form handling.

<div ... data-enhance ...>
    <form ...>
        <!-- NOT enhanced -->
    </form>
</div>

Enhanced form posts only work with Blazor endpoints. Posting an enhanced form to non-Blazor endpoint results in an error.

To disable enhanced form handling:

For an xref:Microsoft.AspNetCore.Components.Forms.EditForm, remove the xref:Microsoft.AspNetCore.Components.Forms.EditForm.Enhance%2A parameter from the form element (or set it to false: Enhance="false").
For an HTML <form>, remove the data-enhance attribute from form element (or set it to false: data-enhance="false").

Blazor's enhanced navigation and form handing may undo dynamic changes to the DOM if the updated content isn't part of the server rendering. To preserve the content of an element, use the data-permanent attribute.

In the following example, the content of the <div> element is updated dynamically by a script when the page loads:

<div data-permanent>
    ...
</div>

To disable enhanced navigation and form handling globally, see xref:blazor/fundamentals/startup#enhanced-navigation-and-form-handling.

For guidance on using the enhancedload event to listen for enhanced page updates, see xref:blazor/fundamentals/routing#enhanced-navigation-and-form-handling.

:::moniker-end

Examples

:::moniker range=">= aspnetcore-8.0"

Examples don't adopt enhanced form handling for form POST requests, but all of the examples can be updated to adopt the enhanced features by following the guidance in the Enhanced form handling section.

:::moniker-end

:::moniker range="< aspnetcore-5.0"

Examples use the target-typed new operator, which was introduced with C# 9.0 and .NET 5. In the following example, the type isn't explicitly stated for the new operator:

public ShipDescription ShipDescription { get; set; } = new();

If using C# 8.0 or earlier (ASP.NET Core 3.1), modify the example code to state the type to the new operator:

public ShipDescription ShipDescription { get; set; } = new ShipDescription();

:::moniker-end

:::moniker range="< aspnetcore-6.0"

Components use nullable reference types (NRTs), and the .NET compiler performs null-state static analysis, both of which are supported in .NET 6 or later. For more information, see xref:migration/50-to-60#nullable-reference-types-nrts-and-net-compiler-null-state-static-analysis.

If using C# 9.0 or earlier (.NET 5 or earlier), remove the NRTs from the examples. Usually, this merely involves removing the question marks (?) and exclamation points (!) from the types in the example code.

The .NET SDK applies implicit global using directives to projects when targeting .NET 6 or later. The examples use a logger to log information about form processing, but it isn't necessary to specify an @using directive for the xref:Microsoft.Extensions.Logging?displayProperty=nameWithType namespace in the component examples. For more information, see .NET project SDKs: Implicit using directives.

If using C# 9.0 or earlier (.NET 5 or earlier), add @using directives to the top of the component after the @page directive for any API required by the example. Find API namespaces through Visual Studio (right-click the object and select Peek Definition) or the .NET API browser.

:::moniker-end

To demonstrate how forms work with data annotations validation, example components rely on xref:System.ComponentModel.DataAnnotations?displayProperty=nameWithType API. If you wish to avoid an extra line of code in components that use data annotations, make the namespace available throughout the app's components with the imports file (_Imports.razor):

@using System.ComponentModel.DataAnnotations

Additional resources

:::moniker range=">= aspnetcore-8.0"

xref:blazor/file-uploads
Blazor samples GitHub repository (dotnet/blazor-samples) (how to download)
ASP.NET Core GitHub repository (dotnet/aspnetcore) forms test assets

:::moniker-end

:::moniker range="< aspnetcore-8.0"

xref:blazor/file-uploads
xref:blazor/security/webassembly/hosted-with-microsoft-entra-id
xref:blazor/security/webassembly/hosted-with-azure-active-directory-b2c
xref:blazor/security/webassembly/hosted-with-identity-server
Blazor samples GitHub repository (dotnet/blazor-samples) (how to download)
ASP.NET Core GitHub repository (dotnet/aspnetcore) forms test assets

:::moniker-end

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index.md

ASP.NET Core Blazor forms overview

Input components and forms

Handle form submission

Clear a form or field

Antiforgery support

Enhanced form handling

Examples

Additional resources

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ASP.NET Core Blazor forms overview

Input components and forms

Handle form submission

Clear a form or field

Antiforgery support

Enhanced form handling

Examples

Additional resources