C# Drag and Drop attached file from outlook email

Question

I want to use/read attached files from an outlook email into a WinForm solution.

Ex: the email has a TXT file attached; I want to perform a Drag&Drog of the TXT file into the WinForm and read the TXT at the same time.

Answer 1

This is an old question, but I'll provide another answer anyhow that doesn't involve using the Outlook objects.

This URL provides working code that is about 13 years old, but still seems to work, on how to handle the "FileGroupDescriptor" and "FileContents" data that Outlook passes to the DropDrop event. Just in case that link dies, here is the relevant code, copy/pasted directly:

DragEnter event:

private void Form1_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
{
  // for this program, we allow a file to be dropped from Explorer
  if (e.Data.GetDataPresent(DataFormats.FileDrop))
  {  e.Effect = DragDropEffects.Copy;}
  //    or this tells us if it is an Outlook attachment drop
  else if (e.Data.GetDataPresent("FileGroupDescriptor"))
  {  e.Effect = DragDropEffects.Copy;}
  //    or none of the above
  else
  {  e.Effect = DragDropEffects.None;}
}

DragDrop event:

private void Form1_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
  string [] fileNames = null;

  try
  {
    if ( e.Data.GetDataPresent(DataFormats.FileDrop,false) == true)
    {
      fileNames = (string []) e.Data.GetData(DataFormats.FileDrop);
      // handle each file passed as needed
      foreach( string fileName in fileNames)
      {
        // do what you are going to do with each filename
      }
    }
    else if (e.Data.GetDataPresent("FileGroupDescriptor"))
    {
      //
      // the first step here is to get the filename
      // of the attachment and
      // build a full-path name so we can store it
      // in the temporary folder
      //

      // set up to obtain the FileGroupDescriptor
      // and extract the file name
      Stream theStream = (Stream) e.Data.GetData("FileGroupDescriptor");
      byte [] fileGroupDescriptor = new byte[512];
      theStream.Read(fileGroupDescriptor,0,512);
      // used to build the filename from the FileGroupDescriptor block
      StringBuilder fileName = new StringBuilder("");
      // this trick gets the filename of the passed attached file
      for(int i=76; fileGroupDescriptor[i]!=0; i++)
      {  fileName.Append(Convert.ToChar(fileGroupDescriptor[i]));}
      theStream.Close();
      string path = Path.GetTempPath();
          // put the zip file into the temp directory
      string theFile = path+fileName.ToString();
          // create the full-path name

      //
      // Second step:  we have the file name.
      // Now we need to get the actual raw
      // data for the attached file and copy it to disk so we work on it.
      //

      // get the actual raw file into memory
      MemoryStream ms = (MemoryStream) e.Data.GetData(
          "FileContents",true);
      // allocate enough bytes to hold the raw data
      byte [] fileBytes = new byte[ms.Length];
      // set starting position at first byte and read in the raw data
      ms.Position = 0;
      ms.Read(fileBytes,0,(int)ms.Length);
      // create a file and save the raw zip file to it
      FileStream fs = new FileStream(theFile,FileMode.Create);
      fs.Write(fileBytes,0,(int)fileBytes.Length);

      fs.Close();  // close the file

      FileInfo tempFile = new FileInfo(theFile);

      // always good to make sure we actually created the file
      if ( tempFile.Exists == true)
      {
        // for now, just delete what we created
        tempFile.Delete();
      }
      else
      {  Trace.WriteLine("File was not created!");}
    }

  }
  catch (Exception ex)
  {
    Trace.WriteLine("Error in DragDrop function: " + ex.Message);

    // don't use MessageBox here - Outlook or Explorer is waiting !
  }

}

Note that this code doesn't Dispose of objects that it should, such as the MemoryStream and FileStream objects.

Answer 2

You can get the running Outlook instance by using the GetActiveObject method which allows to obtain a running instance of the specified object from the running object table (ROT). Then you can automate Outlook to get the currently selected or opened item from which an attachment might be dragged. See C# app automates Outlook (CSAutomateOutlook) for the sample code.