using System;  using System.IO;  string filetomerge=@"C:\temp\data.bin";  string targetpath=@"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", FileMode.Open, FileAccess.Read);  byte[] btArr = new byte[fsr1.Length+fsr2.Length];  fsr1.Read(btArr, 0, 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, 0, btArr.Length);  fsw.Flush();  fsw.Close();