GetMsalGraphToken.cs

private async Task<string> GetTokenAsync(string appId, X509Certificate2 certificate, string tenantId)
{
    var app = ConfidentialClientApplicationBuilder.Create(appId)
                .WithAuthority($"https://login.microsoftonline.com/{tenantId}/")
                .WithCertificate(certificate)
                .Build();

    var scopes = new[] { "https://graph.microsoft.com/.default" };

    var result = await app.AcquireTokenForClient(scopes).ExecuteAsync();
    return result.AccessToken;
}