//.NET's Path.GetTempFilename (https://docs.microsoft.com/en-us/dotnet/api/system.io.path.gettempfilename?view=net-5.0) raises an IOException if the system's temp folder has more than 65535 files

​

//Following a suggestion from https://github.com/dotnet/sdk/issues/8439

//to use Path.GetTempPath (https://docs.microsoft.com/en-us/dotnet/api/system.io.path.gettemppath?view=net-5.0) to get the system temp folder

//combined via Path.Combine (https://docs.microsoft.com/en-us/dotnet/api/system.io.path.combine?view=net-5.0)

//with GetRandomFilename (https://docs.microsoft.com/en-us/dotnet/api/system.io.path.getrandomfilename?view=net-5.0) instead

​

//For extra safety cross-checking (in a do/while loop) with File.Exists (https://docs.microsoft.com/en-us/dotnet/api/system.io.file.exists?view=net-5.0) before returning the file

​

//Using File.WriteAllLines (https://docs.microsoft.com/en-us/dotnet/api/system.io.file.writealllines?view=net-5.0) to create the temp file since that is the original behaviour of GetTempFilename in contrast to GetRandomFilename

​

//Note: "Path.GetRandomFileName() uses the RNGCryptoServiceProvider which is a cryptographically strong random number generator", quoting https://stackoverflow.com/questions/21684696/will-path-getrandomfilename-generate-a-unique-filename-every-time/21684881#21684881

​

using System;

using System.Diagnostics;

using System.IO;

public class Program

{

    public static string Path_SafeGetTempFileName() {

        string filepath; //no need to initialize with empty/null value, the do/while code flow construct will always set a value to filepath

        do

        {

            filepath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

        } while (File.Exists(filepath));

        try

        {

            File.WriteAllLines(filepath, new string[]{}); //generate an empty file

        }

        catch

        {

            Debug.WriteLine($"Couldn't create empty temporary file: {filepath}");

            //TODO: log any failure to generate an empty temp file here

        }

        //Note: don't do a loop if it fails to create the temp file since it might be failing to access the filesystem for other reasons, which would cause infinite recursion

        return filepath;

    }

    public static void Main()

    {

        string tempFilePath1 = Path.GetTempFileName();

        string tempFilePath2 = Path_SafeGetTempFileName();

​

        Console.WriteLine(tempFilePath1);

        Console.WriteLine(tempFilePath2);       

    }

}