GetAccessTokenForUserAsync.cs

protected readonly HttpClient _httpClient;
protected readonly ITokenAcquisition _tokenAcquisition;
protected readonly string _baseUrl = string.Empty;
protected readonly string[] _scopes = Array.Empty<string>();

public ApiService(IConfiguration configuration, ITokenAcquisition tokenAcquisition, HttpClient httpClient)
{
    _httpClient = httpClient;
    _tokenAcquisition = tokenAcquisition;
    _baseUrl = configuration["WebApi:BaseUrl"];
    _scopes = configuration["WebApi:Scopes"].Split(' ');
}

protected async Task PrepareAuthenticatedClient()
{
    string? accessToken;

    try
    {
        accessToken = await _tokenAcquisition.GetAccessTokenForUserAsync(_scopes);
    }
    catch (MsalUiRequiredException)
    {
        accessToken = await _tokenAcquisition.GetAccessTokenForUserAsync(_scopes, 
                    tokenAcquisitionOptions: new TokenAcquisitionOptions { ForceRefresh = true });
    }

    _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
    _httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
}

public async Task<object> Get(string url) 
{
    await PrepareAuthenticatedClient();

    return await _httpClient.GetAsync(url);
}