C#文件合并代码

using System;
using System.IO;
string [email?protected]"C:tempdata.bin";
string [email?protected]"D:store";
string strFileName = filetomerge.Substring(filetomerge.LastIndexOf(Path.DirectorySeparatorChar) + 1);
FileStream fsr1 = new FileStream(targetpath+ Path.DirectorySeparatorChar + strFileName + "1",FileMode.Open,FileAccess.Read);
FileStream fsr2 = new FileStream(targetpath+ Path.DirectorySeparatorChar + strFileName + "2",FileAccess.Read);
byte[] btArr = new byte[fsr1.Length+fsr2.Length];
fsr1.Read(btArr,Convert.ToInt32(fsr1.Length));
fsr2.Read(btArr,Convert.ToInt32(fsr1.Length),Convert.ToInt32(fsr2.Length));
fsr1.Close();
fsr2.Close();
FileStream fsw = new FileStream(%%2 + Path.DirectorySeparatorChar+ strFileName,FileMode.Create,FileAccess.Write);
fsw.Write(btArr,btArr.Length);
fsw.Flush();
fsw.Close();