topic Re: ReadDwgFile from stream in .NET Forum

ReadDwgFile from stream

Ahmadi_rad — Fri, 26 Jun 2020 22:41:06 GMT

Hello

I have a drawing file containing some standard blocks. Using this snippet to read drawing from a memory stream:

using (Stream fs = Assembly.GetExecutingAssembly().GetManifestResourceStream("Resources.StandardBlocks.dwg")) { using (MemoryStream ms = new MemoryStream()) { fs.CopyTo(ms); byte[] bts = ms.ToArray(); GCHandle pinnedArray = GCHandle.Alloc(bts, GCHandleType.Pinned); IntPtr pointer = pinnedArray.AddrOfPinnedObject(); Database sourceDb = new Database(false, true); try { sourceDb.ReadDwgFile(pointer, false, ""); } catch(System.Exception e) { } // Some code to work with sourceDb sourceDb.Dispose(); pinnedArray.Free(); } }

The point is that: when code reaches ReadDwgFile, autocad crashes without even reaching to catch statement.

if it helps, standardBlocks.dwg contains a block of an OLE excel sheet.

Could you please help

Re: ReadDwgFile from stream

artc2 — Sat, 27 Jun 2020 03:12:53 GMT

The ReadDwgFile() method that takes an IntPtr as the first argument expects the IntPtr to be a pointer to an object of one of our internal C++ classes used for reading dwg files. The code static_casts the pointer to that type, so if the object isn't that type, then there will be problems such as what you've experienced.

Re: ReadDwgFile from stream

Ahmadi_rad — Sat, 27 Jun 2020 06:37:51 GMT

thanks for reply

So, How can I use a memory stream for that purpose? I don't directly have a file, whatever it is, it is stored in database or embedded resource in project.

Re: ReadDwgFile from stream

norman.yuan — Sat, 27 Jun 2020 12:00:25 GMT

You would save the Stream as DWG file in the local disk, and then read it into the new Database. You would delete it afterwards, if necessary.

Since your code is AutoCAD add-in and AutoCAD itself uses temporary files a lot. The best practice would be to obtain AutoCAD's temporary file location from current running profile (accessing it via Application.Preferences property), so that your code would have the permission to save/delete temporary file.

Re: ReadDwgFile from stream

Ahmadi_rad — Sun, 28 Jun 2020 11:46:47 GMT

Thanks

I found this post about using preferences object.

But in my visual studio, I can't find class of AcadPreferences as shown in sample. Which dll shall I add to references?

Re: ReadDwgFile from stream

Alexander.Rivilis — Sun, 28 Jun 2020 12:23:54 GMT

I think you can easy use Path.GetTempFileName()