Creating A Temp File In The Temporary directory

Use a specific file name in the temporary directory:

private readonly string testPath = 
    Path.Combine(Path.GetTempPath(), "TestSerializer.xml");

Create a temporary file name in the temporary directory but with a specified extension:

public static class PathClassExtender
{
  public static string GetTempFileName(string newExtension)
  {
    string res = Path.ChangeExtension(Path.GetTempFileName(), newExtension);
    return res;
  }
}

Sample usage:

string filename = PathClassExtender.GetTempFileName(".bat");

filename will get set to something like
"C:\Users\RB\AppData\Local\Temp\tmp517F.bat"