example dotnet 6 code to sign an apple JWT from p8 certificate file

example.cs

	public class TokenSigningRequest
	{
	public string AppleTeamId { get; set; }
	public string AppleServiceId { get; set; }
	public string AppleKeyId { get; set; }
	public string P8key { get; set; }
	}

	[HttpPost]
	public async Task<IActionResult> CreateSignedToken([FromBody, BindRequired] TokenSigningRequest requestBody)
	{
	string audience = "https://appleid.apple.com";

	string issuer = requestBody?.AppleTeamId;
	string subject = requestBody?.AppleServiceId;
	string kid = requestBody?.AppleKeyId;
	string p8key = requestBody?.P8key;

	IList<Claim> claims = new List<Claim> {
	new Claim ("sub", subject)
	};
	using (ECDsa key = ECDsa.Create())
	{
	key.ImportPkcs8PrivateKey(Convert.FromBase64String(p8key), out _);

	// CngKey cngKey = CngKey.Import(Convert.FromBase64String(p8key), CngKeyBlobFormat.Pkcs8PrivateBlob);

	SigningCredentials signingCred = new SigningCredentials(
	new ECDsaSecurityKey(key),
	SecurityAlgorithms.EcdsaSha256
	);

	JwtSecurityToken token = new JwtSecurityToken(
	issuer,
	audience,
	claims,
	DateTime.Now,
	DateTime.Now.AddDays(180),
	signingCred
	);
	token.Header.Add("kid", kid);
	token.Header.Remove("typ");

	JwtSecurityTokenHandler tokenHandler = new JwtSecurityTokenHandler();

	string jwt = tokenHandler.WriteToken(token);

	return (ActionResult)new OkObjectResult(new
	{
	token = jwt
	});
	}
	}