Trim BOM (Byte Order Mark) from text.

TrimBom.cs

public static string TrimBom(string text, Encoding encoding)
{
    var bom = encoding.GetPreamble();
    if (bom.Length < 1)
    {
        return text;
    }

    var textBytes = Convert.FromBase64String(text);
    if (!textBytes.Take(bom.Length).SequenceEqual(bom))
    {
        return text;
    }

    var trimmedBytes = textBytes.Skip(bom.Length).ToArray();
    return encoding.GetString(trimmedBytes);
}