php中获取sha256编码为：

hash("sha256", "123456")

结果为：

8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92

C#中获取sha256的代码为：

/// <summary>
    /// Sha256编码（模拟php中 hash('sha256', $str)）
    /// </summary>
    /// <param name="str">要编码的字符</param>
    /// <returns>返回编码过的字符</returns>
    public string ToSha256(string str)
    {
        byte[] bytes = Encoding.UTF8.GetBytes(str);
        System.Security.Cryptography.HashAlgorithm algorithm = new System.Security.Cryptography.SHA256Managed();
        return BitConverter.ToString(algorithm.ComputeHash(bytes)).Replace("-", "").ToLower();
    }

运行结果同样为：

8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92