Target class [DashboardController] does not exist code example

Example 1: Target class [UserController] does not exist.

Note: don't forget to import (use) your controller in the routes(web.php) file at the top. Like:
use App\Http\Controllers\PagesController;

Route::get('/',[PagesController::class, 'index']);

Example 2: Target class [Controller] does not exist.

//accessing any function in the controller (this is web.php file)
use App\Http\Controllers\PostsController;

Route::get('/post', 'App\Http\Controllers\PostsController@index');

Example 3: laravel target class does not exist

Uncomment this line in app>>provider>>RouteServiceProvider.php file
// protected $namespace = 'App\\Http\\Controllers';