CryptSignHash

[DllImport("Advapi32.dll", SetLastError = true)][return: MarshalAs(UnmanagedType.Bool)]
public static extern bool CryptSignHash(
   IntPtr hHash,
   uint dwKeySpec,
   string sDescription,
   uint dwFlags,
   byte[] pbSignature,
   ref uint pdwSigLen
);

Microsoft documentation: Link