vc ++中字节文件的大小

Question

FileStream^ fs = File::OpenRead("C:\\example.bin");
array<Byte>^ b = gcnew array<Byte>(1000);
fs->Read(b,0,1000);

unsigned char *pb;
pb=(byte*)malloc(1000);
Marshal::Copy(b,0,IntPtr(pb),1000);

res=Send(pb, b->Length);

我想以字节为单位使用文件 example.bin 的大小而不是值1000.我该怎么办？