View-based authorization

A developer often wants to show, hide, or otherwise modify a UI based on the current user identity. You can access the authorization service within MVC views via dependency injection. To inject the authorization service into a Razor view, use the @inject directive:

@using Microsoft.AspNetCore.Authorization
@inject IAuthorizationService AuthorizationService

If you want the authorization service in every view, place the @inject directive into the _ViewImports.cshtml file of the Views directory. For more information, see Dependency injection into views.

Use the injected authorization service to invoke AuthorizeAsync in exactly the same way you would check during resource-based authorization:

@if ((await AuthorizationService.AuthorizeAsync(User, "PolicyName")).Succeeded)
{
    <p>This paragraph is displayed because you fulfilled PolicyName.</p>
}

In some cases, the resource will be your view model. Invoke AuthorizeAsync in exactly the same way you would check during resource-based authorization:

@if ((await AuthorizationService.AuthorizeAsync(User, Model, Operations.Edit)).Succeeded)
{
    <p><a class="btn btn-default" role="button"
        href="@Url.Action("Edit", "Document", new { id = Model.Id })">Edit</a></p>
}

In the preceding code, the model is passed as a resource the policy evaluation should take into consideration.

Warning

Don't rely on toggling visibility of your app's UI elements as the sole authorization check. Hiding a UI element may not completely prevent access to its associated controller action. For example, consider the button in the preceding code snippet. A user can invoke the Edit action method if he or she knows the relative resource URL is /Document/Edit/1. For this reason, the Edit action method should perform its own authorization check.