How can I create a temp file with a specific extension with .NET?

Question

I need to generate a unique temporary file with a .csv extension.

What I do right now is

string filename = System.IO.Path.GetTempFileName().Replace(         


        

Answer 1

Easy Function in C#:

public static string GetTempFileName(string extension = "csv")
{
    return Path.ChangeExtension(Path.GetTempFileName(), extension);
}

Answer 2

Why not checking if the file exists?

string fileName;
do
{
    fileName = System.IO.Path.GetTempPath() + Guid.NewGuid().ToString() + ".csv";
} while (System.IO.File.Exists(fileName));

Answer 3

public static string GetTempFileName(string extension)
{
  int attempt = 0;
  while (true)
  {
    string fileName = Path.GetRandomFileName();
    fileName = Path.ChangeExtension(fileName, extension);
    fileName = Path.Combine(Path.GetTempPath(), fileName);

    try
    {
      using (new FileStream(fileName, FileMode.CreateNew)) { }
      return fileName;
    }
    catch (IOException ex)
    {
      if (++attempt == 10)
        throw new IOException("No unique temporary file name is available.", ex);
    }
  }
}

Note: this works like Path.GetTempFileName. An empty file is created to reserve the file name. It makes 10 attempts, in case of collisions generated by Path.GetRandomFileName();

Answer 4

How about:

Path.Combine(Path.GetTempPath(), DateTime.Now.Ticks.ToString() + "_" + Guid.NewGuid().ToString() + ".csv")

It is highly improbable that the computer will generate the same Guid at the same instant of time. The only weakness i see here is the performance impact DateTime.Now.Ticks will add.

Answer 5

I mixed @Maxence and @Mitch Wheat answers keeping in mind I want the semantic of GetTempFileName method (the fileName is the name of a new file created) adding the extension preferred.

string GetNewTempFile(string extension)
{
    if (!extension.StartWith(".")) extension="." + extension;
    string fileName;
    bool bCollisions = false;
    do {
        fileName = Path.Combine(System.IO.Path.GetTempPath(), Guid.NewGuid().ToString() + extension);
        try
        {
            using (new FileStream(fileName, FileMode.CreateNew)) { }
            bCollisions = false;
        }
        catch (IOException)
        {
            bCollisions = true;
        }
    }
    while (bCollisions);
    return fileName;
}