programmatically update a file in document library

Wondering how to how to update file in document library? Well, if you want to programmatically update a document and save it back to the document library.. here is the code for that

public void UpdateDocument()
{
 System.Text.ASCIIEncoding enc = new System.Text.ASCIIEncoding();

 SPSecurity.RunWithElevatedPrivileges(delegate()
 {
  using (SPSite siteColl = new SPSite("http://localhost:8080/"))
  {
   using (SPWeb web = siteColl.OpenWeb())
   {
    try
    {   
     SPFile spfile = web.GetFile("http://localhost:8080/Lists/DemoLib/abc.txt");
     if (spfile.Exists)
     {
      byte[] byteArrayFileContentsBefore = spfile.OpenBinary();

      if (byteArrayFileContentsBefore.Length > 0)
      {
       string strFileContentsBefore = enc.GetString(byteArrayFileContentsBefore); //convert byte array to string.
       string newStr = strFileContentsBefore + "This is the new text added";
       byte[] byteArrayFileContentsAfter = null;
       if (!newStr.Equals(""))
       {
        byteArrayFileContentsAfter = enc.GetBytes(newStr);
        spfile.SaveBinary(byteArrayFileContentsAfter); //save to the file.
       }
      }
     }
    }
    catch (Exception e){}
   } 
  }
 });
}

SPFile has a CopyFile method which can copy the file to a new location. But if there was an existing file on the new location, you can set the overwrite parameter to true to overwrite it. Here is a problem, supposingly there was a workflow already on the file in the new location... when you use CopyFile.. the workflow is lost.. basically it is not an update of the file.. it is infact a delete and re-adding of the file. The following code will overcome this problem

private void UpdateDocumentForERB_ExecuteCode(SPWeb web, string originalFileUrl, string targetFileUrl)
{
 SPSecurity.RunWithElevatedPrivileges(delegate()
 {
  SPFile OriFile = web.GetFile(originalFileUrl);
  SPFile TarFile = web.GetFile(targetFileUrl);

  byte[] byteArrayOriFile = OriFile.OpenBinary();

  TarFile.SaveBinary(byteArrayOriFile);

 });

}