在C#中解码Javascript FileReader Base64

using System;
using System.IO;

public class Base64Decoder
{
    public static byte[] DecodeBase64String(string base64String)
    {
        try
        {
            // 解码Base64字符串
            byte[] data = Convert.FromBase64String(base64String);
            return data;
        }
        catch (FormatException e)
        {
            Console.WriteLine("The input is not a valid Base64 string.");
            Console.WriteLine(e.Message);
            return null;
        }
    }

    public static void Main()
    {
        string base64String = "SGVsbG8sIFdvcmxkIQ=="; // 示例Base64编码的字符串
        byte[] decodedData = DecodeBase64String(base64String);

        if (decodedData != null)
        {
            Console.WriteLine("Decoded data length: " + decodedData.Length);
        }
    }
}

using System.Text.RegularExpressions;

public static bool IsValidBase64String(string base64String)
{
    // 正则表达式验证Base64字符串
    string base64Pattern = @"^[A-Za-z0-9+/]*={0,2}$";
    return Regex.IsMatch(base64String, base64Pattern);
}

if (IsValidBase64String(base64String))
{
    byte[] decodedData = DecodeBase64String(base64String);
    // 处理解码后的数据
}
else
{
    Console.WriteLine("Invalid Base64 string.");
}