How do I automatically delete temp files in C#?

Nothing is guaranteed if the process is killed prematurely, however, I use "using" to do this..

using System;
using System.IO;
sealed class TempFile : IDisposable
{
    string path;
    public TempFile() : this(System.IO.Path.GetTempFileName()) { }

    public TempFile(string path)
    {
        if (string.IsNullOrEmpty(path)) throw new ArgumentNullException("path");
        this.path = path;
    }
    public string Path
    {
        get
        {
            if (path == null) throw new ObjectDisposedException(GetType().Name);
            return path;
        }
    }
    ~TempFile() { Dispose(false); }
    public void Dispose() { Dispose(true); }
    private void Dispose(bool disposing)
    {
        if (disposing)
        {
            GC.SuppressFinalize(this);                
        }
        if (path != null)
        {
            try { File.Delete(path); }
            catch { } // best effort
            path = null;
        }
    }
}
static class Program
{
    static void Main()
    {
        string path;
        using (var tmp = new TempFile())
        {
            path = tmp.Path;
            Console.WriteLine(File.Exists(path));
        }
        Console.WriteLine(File.Exists(path));
    }
}

Now when the TempFile is disposed or garbage-collected the file is deleted (if possible). You could obviously use this as tightly-scoped as you like, or in a collection somewhere.

You could P/Invoke CreateFile and pass the FILE_FLAG_DELETE_ON_CLOSE flag. This tells Windows to delete the file once all handles are closed. See also: Win32 CreateFile docs.

I'm not primarily a C# programmer, but in C++ I'd use RAII for this. There are some hints on using RAII-like behaviour in C# online, but most seem to use the finalizer — which is not deterministic.

I think there are some Windows SDK functions to create temporary files, but don't know if they are automatically deleted on program termination. There is the GetTempPath function, but files there are only deleted when you log out or restart, IIRC.

P.S. The C# destructor documentation says you can and should release resources there, which I find a bit odd. If so, you could simply delete the temp file in the destructor, but again, this might not be completely deterministic.

It's nice to see that you want to be responsible, but if the files aren't huge (>50MB), you would be in line with everyone (MS included) in leaving them in the temp directory. Disk space is abundant.

As csl posted, GetTempPath is the way to go. Users who are short on space will be able to run disk cleanup and your files (along with everyone else's) will be cleaned up.

You could launch a thread on startup that will delete files that exist when they "shouldn't" to recover from your crash.