[WebMethod]
public byte[] DownloadFile(string FName)
{
System.IO.FileStream fs1=null;
fs1=System.IO.File.Open(FName,FileMode.Open,FileAccess.Read);
byte[] b1=new byte[fs1.Length];
fs1.Read(b1,0,(int)fs1.Length);
fs1.Close();
return b1;
}
Use the following reference code, hopefully it will helpful for you.