I am using a library to create a PDF file from HTML, then I print that file and delete it from disk. The issue is, we don't want anything stored on disk, not even temporarily. I thought about using some kind of RamDisk, but I see MemoryMappedFile thrown around everywhere. I looked into it, but I don't think that provides the functionality I want since the file should already exist on disk before using it in a MemoryMappedFile.
My question is: Is my assumption true about the file needing to be on disk FIRST before using it in a MemoryMappedFile? IS there a way to create a MemoryMappedFile and access it using a virtual path without it existing on disk?
In case MemoryMappedFile doesn't work, what library can I use to create a virtual RamDisk with C#? It will only be storing 1 file at a time.
Related
I have two method Save() and Load() of different classes. Both method have overload of 'String' and "Stream".
Could someone tell me how to save the data from one class using the save method and load to different class without creating any temp file?
Have a look at Memory-Mapped files especially at the non-persisted files section.
Non-persisted files are memory-mapped files that are not associated
with a file on a disk. When the last process has finished working with
the file, the data is lost and the file is reclaimed by garbage
collection. These files are suitable for creating shared memory for
inter-process communications (IPC).
I'm working in c#, and looking for a way to create a path to a directory that will map to an IO.Stream instead of to the actual file system.
I want to be able to "save" files to that path, manipulate the content or file names, and then save them from that path to a regular file in the file system.
I know I can use a temporary file, but I would rather use the memory for both security and performance.
This kind of thing exists, according to this answer, in Java, using the FileSystemProvider class. I'm looking for a way to do it in c#.
I've tried every search I could think of and came up only with the java answer and suggestions to use Temporary files.
Is it even possible using .net?
Basically, I'm looking for a way to enable saving files directly to memory as if they where saved into the file system.
so, for instance, if I had a 3rd party class that exposes a save method (save(string fullPath)), or something like the SmtpServer.Send(MyMsg) in this question, i could choose that path and save it into the memory stream instead of onto the drive. (the main thing here is that I want to provide a path that will lead directly to a memory stream).
.NET doesn't have an abstraction layer over the host OS's file system. So unless you can build your own for use in custom code, and you need to have 3rd party libraries covered, there are just two workable optilns:
Use streams and avoid any APIs working with file names.
Build a virtual file system plugged into your host OS's storage architecture; however, the effort needed versus benefits is highly questionable.
I went through a similar situation lately, and there is no out of the box solution in .NET for doing that although I used a workaround which was efficient and safe for me.
Using Ionic.Zip Nuget package you can create a whole directory with a complex structure as a stream in memory and although it will be created as a zip file, you can extract it as a stream or even send the zip file as a stream.
using (var zip = new Ionic.Zip.ZipFile())
{
zip.AddEntry($"file1.json", new MemoryStream(Encoding.UTF8.GetBytes(someJsonContent)));
for (int i = 0; i < 4; i++)
{
zip.AddEntry($"{myDir}/{i}.json", new MemoryStream(Encoding.UTF8.GetBytes(anotherJsonContent)));
}
}
And here is how to extract a zip file as a stream using Ionic.Zip
I'm trying to create a program that has the capability of creating a zipped package containing files based on user input.
I don't need any of those files to be written to the hard drive before they're zipped, as that would be unnecessary, so how do I create these files without actually writing them to the hard drive, and then have them zipped?
I'm using DotNetZip.
See the documentation here, specifically the example called "Create a zip using content obtained from a stream":
using (ZipFile zip = new ZipFile())
{
ZipEntry e= zip.AddEntry("Content-From-Stream.bin", "basedirectory", StreamToRead);
e.Comment = "The content for entry in the zip file was obtained from a stream";
zip.AddFile("Readme.txt");
zip.Save(zipFileToCreate);
}
If your files are not already in a stream format, you'll need to convert them to one. You'll probably want to use a MemoryStream for that.
I use SharpZipLib, but if DotNetZip can do everything against a basic System.IO.Stream, then yes, just feed it a MemoryStream to write to.
Writing to the hard disk shouldn't be something avoid because it's unnecessary. That's backwards. If it's not a requirement that the entire zipping process is done in memory then avoid it by writing to the hard disk.
The hard disk is better suited for storing large amounts of data than memory is. If by some chance your zip file ends up being around a gigabyte in size your application could croak or at least cause a system slowdown. If you write directly to the hard drive the zip could be several gigabytes in size without causing an issue.
I was using the Microsoft.Office.Interop.Excel in C# to create a custom .xlsx file.
In doing so I created a Workbook object. Due to the nature of complex SQL queries to grab the data, process it, and apply via Interop the custom styles and formatting the code is very lengthy. Not to mention the very careful process of avoiding memory leaks from the Interop itself, and ensuring that Excel actually closes properly after running.
I originally was testing it out as a console application, and got it working to my satisfaction. What it does is save the end result to the filesystem using the SaveAs member.
However, my next goal was to instead redirect the output as an output stream to asp.net similar to this question here. I've done some rudimentary research and I cannot seem to find an approach that does not involve first saving the Workbook to the server's file system. This may cause conflicts if several users are accessing at the same time, etc.
So my question is, is there an easy way to set the asp.net ContentType for .xlsx and stream out the Workbook object without saving it to the file system? If not, is there a way asp.net can save temporary files automatically without conflicts, serve the temp file, and then delete the temp file after it's been served?
I agree with the comments that you should avoid using Excel Interop server-side, and the third party libraries I've used (EPPlus, Aspose) all support streaming the output. However, if you want to save temporary files without conflict you can use Path.GetTempFileName.
If your ASP.NET app is running under an account without a profile, you may need to give it write access to %WINDIR%\Temp or whatever temporary directory it uses.
Is it possible to create a file on a disk which is full??
Does creation of the file take any space??
Basically I am seeing a case where C# has created but failed to write anything whhich I think points to a full disk.
Does anyone know whether creating a file on a full disk will fail or not??
This wa done using c# o Windw xSerevr- The log file was also written to the same drive
Creating (empty) files should still be possible in most cases. The MFT is a separate part of the volume which won't get used for file data.
It should even be possible to store small amounts of data without needing more than the file entry in the MFT. NTFS can store streams as "resident data" in the stream descriptor which doesn't need any additional space, but only works for very small files.
I think your issue is another problem, though. It may be that you have permissions to create a file but not to write anything to it. You might want to check the ACLs of the location where you're trying to write.