How to return azure blob storage fileas FileStreamResult?

I am developing web api for work with files. I am trying to download file from azure blob storage and return it as response. For development api I using FastEndpoints.

On SO I found out that the best option is to use FileStreamResult, but I am gettign error

System.NotSupportedException: Deserialization of types without a
parameterless constructor

How can I resolve it and why I am facing it?

Endpoint

public class Endpoint : Endpoint<DownloadFileRequest, FileStreamResult>
{
    private readonly DatabaseContext _context;
    private readonly ILogger _logger;
    private readonly IConfiguration _configuration;

    public Endpoint(DatabaseContext context, ILogger<Endpoint> logger, IConfiguration configuration)
    {
        _context = context;
        _logger = logger;
        _configuration = configuration;
    }

    public override void Configure()
    {
        Get("/file/{id}/download");
        Roles(Role.Administrator, Role.ProjectManager, Role.GraphicDesigner, Role.Accountant);
        Description(b => b.WithName("DownloadFile"));
    }

    public override async Task HandleAsync(DownloadFileRequest r, CancellationToken c)
    {
        var file = await Data.GetTriadaFileAsync(_context, r.Id, c); // gets file to 
                                                                     // download

        if (file == null)
        {
            await SendNotFoundAsync(c);
            return;
        }
           
        var result = await Data.DownloadBlobAsync(file.AzureName, r, c, _configuration);

        if (result != null)
        {
            Response.FileStream = result.FileStream;
        }
    }
}

Data

public static class Data
{
    public static async Task<TriadaFile?> GetTriadaFileAsync(DatabaseContext context, Guid id, CancellationToken c)
    {
        return await context.Files
            .FirstOrDefaultAsync(x => x.Id == id, c);
    }
    public static async Task<FileStreamResult?> DownloadBlobAsync(string blobFileName, DownloadFileRequest r, CancellationToken c, IConfiguration _configuration)
    {
        string connectionString = _configuration.GetSection("Azure").GetValue<string>("BlobConnectionString")!;
        string containerName = _configuration.GetSection("Azure").GetValue<string>("BlobContainerName")!;

        BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);
        BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(containerName);

        BlobClient blobClient = containerClient.GetBlobClient(blobFileName);

        using (var stream = new MemoryStream())
        {
            await blobClient.DownloadToAsync(stream);
            stream.Position = 0;
            var contentType = (await blobClient.GetPropertiesAsync()).Value.ContentType;

            var fileStreamResult = new FileStreamResult(stream, "application/octet-stream");

            fileStreamResult.FileDownloadName = blobFileName;

            return fileStreamResult;
        }
    }


}

Models

public class DownloadFileRequest
{
    public Guid Id{ get; set; }
}

public class Validator : Validator<DownloadFileRequest>
{
    public Validator()
    {
        RuleFor(x => x.Id)
            .NotEmpty();
    }
}

public class DownloadFileResponse
{
   

}

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