c# 读取文件，一次可以读取多少个字节数组，我有一个文件，内容差不多是1000万个字节，该怎么读？？？？

string sFilePath=@"D:\\Test\\datfil.txt";
FileStream fileStream = new FileStream(sFilePath, FileMode.Open, System.IO.FileAccess.Read);
byte[] byteRecord = new byte[1000];
long lSize = fileStream.Length;
long lReadTimes = lSize /1000;
int iTemp = lSize %1000;
fileStream.Seek(0, SeekOrigin.Begin);
for (int i = 1; i <= lReadTimes ; i++)
{
fileStream.Read(byteRecord, 0, 1000);
}
fileStream.Read(byteRecord, 0, iTemp );

string s = File.ReadAllText("D:\\123.txt", Encoding.Default);

string[] s = File.ReadAllLines("D:\\123.txt", Encoding.Default);

2选一