问题在于您正在读取一个二进制文件，而 streamreader 在将其读入 Unicode 字符串时会进行一些解释.需要按字节处理.

The problem is that you are reading in a binary file and the streamreader does some interpretation when it reads it into a Unicode string. It needed to be dealt with as bytes.

我的代码如下.(仅供参考，您需要启用不安全编译来编译代码 - 这是为了快速搜索二进制数组)

My code is below.(Just as an FYI, you will need to enable unsafe compilation to compile the code - this was to allow a fast search of the binary array)

只是为了适当的归属，我从这个 SO answer 借用了 IndexOf 的字节版本迪伦·尼科尔森

Just for proper attribution, I borrowed the byte version of IndexOf from this SO answer by Dylan Nicholson

namespace ArkIndex
{
    class Program
    {
        static void Main(string[] args)
        {
            string fileName = "TheIsland.ark";
            string searchString = "TamedName";
            byte[] bytes = LoadBytesFromFile(fileName);
            byte[] searchBytes = System.Text.ASCIIEncoding.Default.GetBytes(searchString);

            List<long> allNeedles = FindAllBytes(bytes, searchBytes);    
        }

        static byte[] LoadBytesFromFile(string fileName)
        {
            FileStream fs = new FileStream(fileName, FileMode.Open);
            //BinaryReader br = new BinaryReader(fs);
            //StreamReader ff = new StreamReader(fileName);

            MemoryStream ms = new MemoryStream();
            fs.CopyTo(ms);
            fs.Close();
            return ms.ToArray();   
        }

        public static List<long> FindAllBytes(byte[] haystack, byte[] needle)
        {
            long currentOffset = 0;
            long offsetStep = needle.Length;
            long index = 0;
            List<long> allNeedleOffsets = new List<long>();
            while((index = IndexOf(haystack,needle,currentOffset)) != -1L)
            {
                allNeedleOffsets.Add(index);
                currentOffset = index + offsetStep;
            }
            return allNeedleOffsets;
        }

        public static unsafe long IndexOf(byte[] haystack, byte[] needle, long startOffset = 0)
        {
            fixed (byte* h = haystack) fixed (byte* n = needle)
            {
                for (byte* hNext = h + startOffset, hEnd = h + haystack.LongLength + 1 - needle.LongLength, nEnd = n + needle.LongLength; hNext < hEnd; hNext++)
                    for (byte* hInc = hNext, nInc = n; *nInc == *hInc; hInc++)
                        if (++nInc == nEnd)
                            return hNext - h;
                return -1;
            }
        }    
    }
}