System.Waf.Applications.RecentFileList.AddFile C# (CSharp) Method

        public void AddFile(string fileName)
        {
            if (string.IsNullOrEmpty(fileName)) { throw new ArgumentException("The argument fileName must not be null or empty.", nameof(fileName)); }

            RecentFile recentFile = recentFiles.FirstOrDefault(r => r.Path == fileName);
            
            if (recentFile != null)
            {
                int oldIndex = recentFiles.IndexOf(recentFile);
                int newIndex = recentFile.IsPinned ? 0 : PinCount;
                if (oldIndex != newIndex)
                {
                    recentFiles.Move(oldIndex, newIndex);
                }
            }
            else
            {
                if (PinCount < maxFilesNumber)
                {
                    if (recentFiles.Count >= maxFilesNumber)
                    {
                        RemoveAt(recentFiles.Count - 1);
                    }
                    Insert(PinCount, new RecentFile(fileName));
                }
            }
        }

        public void SetMaxFilesNumber()
        {
            RecentFileList recentFileList = new RecentFileList();
            recentFileList.AddFile("Doc4");
            recentFileList.AddFile("Doc3");
            recentFileList.AddFile("Doc2");
            recentFileList.AddFile("Doc1");
            Assert.IsTrue(recentFileList.RecentFiles.Select(f => f.Path).SequenceEqual(new [] { "Doc1", "Doc2", "Doc3", "Doc4" }));
            
            // Set a lower number than items are in the list => expect that the list is truncated.
            recentFileList.MaxFilesNumber = 3;
            Assert.AreEqual(3, recentFileList.MaxFilesNumber);
            Assert.IsTrue(recentFileList.RecentFiles.Select(f => f.Path).SequenceEqual(new[] { "Doc1", "Doc2", "Doc3" }));

            AssertHelper.ExpectedException<ArgumentException>(() => recentFileList.MaxFilesNumber = -3);
        }