C# xml報文摘要計算

public static string EncryptToSHA1(string str)
{
SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
byte[] str1 = Encoding.UTF8.GetBytes(str);
byte[] str2 = sha1.ComputeHash(str1);
sha1.Clear();
(sha1 as IDisposable).Dispose();
return Convert.ToBase64String(str2);
}這個方法用來計算摘要值是否正確？   另外能否給個簡單的報文并給出其摘要值····