C# md5 and sha1 crypt

EncryptHelper.cs

using System;
using System.Security.Cryptography;
using System.Text;

namespace Demo
{
    public static class Md5Encrypt
    {
        /// <summary>
        /// 获取由MD5加密的字符串
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static string EncryptToMd5(string str)
        {
            var md5 = new MD5CryptoServiceProvider();
            return Encrypt(md5, str);
        }

        /// <summary>
        /// 获取由SHA1加密的字符串
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static string EncryptToSha1(string str)
        {
            var sha1 = new SHA1CryptoServiceProvider();
            return Encrypt(sha1, str);
        }

        private static string Encrypt(HashAlgorithm cryptProvider, string str)
        {
            if (cryptProvider != null && !string.IsNullOrEmpty(str))
            {
                byte[] str1 = Encoding.UTF8.GetBytes(str);
                byte[] str2 = cryptProvider.ComputeHash(str1, 0, str1.Length);
                cryptProvider.Clear();
                cryptProvider.Dispose();
                return Convert.ToBase64String(str2);
            }
            return string.Empty;
        }
    }
}