C#十六进制数据流文件读取

string path = @"NS_240.dat"; //文件路径
FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read); //建立Filestream
BinaryReader br = new BinaryReader(fs); //建立BinaryReader
byte[] bytData;
StringBuilder sb = new StringBuilder();
for (int i = 100; i < 3000 * 240; i = i + 3000)
{
br.BaseStream.Position = i;
bytData = br.ReadBytes(300);
sb.Append = bytData.ToString("X2");
}
Console.WriteLine(sb);
Console.Read();
想实现数据流在100个字节处开始读取300个，然后在3100个处再读300个，结果程序debug后仅能出现System.Byte[]
求问为什么？？

用FOR一个一个的读
sb.Append支持char,