Base64 encode and decode UTF-8 text safely

using System;
using System.Text;

static string ToBase64(string text) => Convert.ToBase64String(Encoding.UTF8.GetBytes(text));

static string FromBase64(string encoded)
{
    if (encoded.Length == 0 || encoded.Length % 4 != 0)
        throw new FormatException("Base64 length must be a non-zero multiple of 4.");
    try
    {
        return Encoding.UTF8.GetString(Convert.FromBase64String(encoded));
    }
    catch (FormatException ex)
    {
        throw new FormatException($"Invalid Base64: {ex.Message}", ex);
    }
}