二进制转成字符

public static string ToHexString(byte[] bytes)
{
    string str = string.Empty;
    if (bytes == null)
    {
        return str;
    }
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < bytes.Length; i++)
    {
        builder.Append(bytes[i].ToString("X2"));
    }
    return builder.ToString();
}