Creating something from nothing [Developer-friendly virtual file implementation for .NET!]

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Comments

• Anonymous
  March 24, 2012
  The comment has been removed

• Anonymous
  March 26, 2012
  Robinson, This is probably just an artifact of running under the debugger - please have a look at the following comment and my reply (search for "Tyler" if your browser doesn't scroll to it automatically): blogs.msdn.com/.../creating-something-from-nothing-asynchronously-developer-friendly-virtual-file-implementation-for-net-improved.aspx Hope this helps!

• Anonymous
  October 06, 2012
  Curious as to how to know the resulting path that was created after the drop operation is complete? Possible?

• Anonymous
  October 06, 2012
  Justin, Offhand, I'm not sure that's easily available. Here's a post Raymond Chen did on the topic that may be helpful to understand why: blogs.msdn.com/.../2453927.aspx

• Anonymous
  December 17, 2012
  Many thanks. It works for Windows Explorer. Is there somewhere to see how to process drop of the dragged file. I noticed that this way (www.codeproject.com/.../Outlook-Drag-and-Drop-in-C) it does not work right, although it works when drop is from Outlook.

• Anonymous
  December 18, 2012
  Alex Nossov, I don't know offhand, but if you're implementing a streaming approach, then the code that streams the file should know how far it has gone and how far it has left and may be able to communicate the progress out to someone somehow. Just a thought - I hope it's helpful!

• Anonymous
  December 19, 2012
  David, thanks, my question was very simple. I am trying to figure out, why the code below works fine when drop is from MS Outlook, but it reads 26 zeros, if drop is from your test application, "Virtual File" box was dragged and droped to my application.                case TYMED.TYMED_ISTREAM:                    //to handle a IStream it needs to be read into a managed byte and                    //returned as a MemoryStream                    IStream iStream = null;                    System.Runtime.InteropServices.ComTypes.STATSTG iStreamStat;                    try                    {                        //marshal the returned pointer to a IStream object                        iStream = (IStream)Marshal.GetObjectForIUnknown(medium.unionmember);                        Marshal.Release(medium.unionmember);                        //get the STATSTG of the IStream to determine how many bytes are in it                        iStreamStat = new System.Runtime.InteropServices.ComTypes.STATSTG();                        iStream.Stat(out iStreamStat, 0);                        int iStreamSize = (int)iStreamStat.cbSize;                        //read the data from the IStream into a managed byte array                        byte[] iStreamContent = new byte[iStreamSize];                        iStream.Read(iStreamContent, iStreamContent.Length, IntPtr.Zero);                        //wrapped the managed byte array into a memory stream and return it                        return new MemoryStream(iStreamContent);                    }                    finally                    {                        //release all unmanaged objects                        Marshal.ReleaseComObject(iStream);                    } So, iStreamContent gets only 26 of 0 values, instead of "abc.... " I've checked that delegate code assigned to StreamContents in your app is called and generate right "var contents =..." . Please, let me know, what can help, or if I ask too much :)

• Anonymous
  December 20, 2012
  Alex Nossov, I'm not familiar with IStream, so I looked it up and landed here for the Read method: msdn.microsoft.com/.../aa380011(v=vs.85).aspx That calls out two things from your example:

1. The pcbRead parameter is required, but the code above passes NULL
2. The return value from the call is not checked My guess is that it's returning STG_E_INVALIDPOINTER because of the NULL - I'm not confident in that guess, but it's definitely where I'd start looking. Hope this helps!

• Anonymous
  March 19, 2014
  Hi i am getting bytes of file from database so how can i achieve this in StreamContents action? StreamContents = stream =>            {                 data=///Here i want to get the data from DB but it is not executing,any idea ??                 stream.Write(data, 0, data.Length);            }

• Anonymous
  March 20, 2014
  Sagar, I'm not sure what you mean by "not executing". Whatever your "data" object is needs to be able to request information from the database and then write it to the "stream" parameter of the lambda. For a similar example, have a look at the TextUrlVirtualFile_MouseButtonDown method in the sample - it downloads from a web site and streams the content. Hope this helps!

• Anonymous
  March 20, 2014
  Hi David, yes i have went through that TextUrlVirtualFile_MouseButtonDown method, where its downloading using webclient, but in my case when any listview item is dragged that time i have only guid of that file, then later i get that byte data of that respective file from database and the i pass this byte array to stream parameter, So if i perform the Getting data from Database before creating stream then cursor doesnt changes as byte are not retrieved, so i want to perform this getdatafromDB operation here in this block StreamContents = stream =>           {                data=GetDataFromDataBase();//Is it Correct? or Is it possible to perform the operation when drop happens then get the data from DB and then pass it to stream parameter??                stream.Write(data, 0, data.Length);           }

• Anonymous
  March 24, 2014
  Sagar, I'm not sure I understand your scenario/configuration, but what you show above seems right to me.