public CollectionChangedTestViewModel()
        {
            HeaderText.Value = "Section1";
            FooterText.Value = "FooterText1";

            var headers = new string[] { "Hoge", "Fuga", "Piyo" };
            var footers = new string[] { "Fumufumu", "Houhou", "Naninai" };

            var idxH = 0;
            var idxF = 0;

            SectionCommand.Subscribe(p => {
                if (p == "Header")
                {
                    HeaderText.Value = headers[idxH++];
                    if (idxH >= 3)
                    {
                        idxH = 0;
                    }
                }
                else
                {
                    FooterText.Value = footers[idxF++];
                    if (idxF >= 3)
                    {
                        idxF = 0;
                    }
                }
            });
        }
        public CollectionChangedTestViewModel()
        {
            HeaderText.Value = "Section1";
            FooterText.Value = "FooterText1";

            var headers = new string[] { "Hoge", "Fuga", "Piyo" };
            var footers = new string[] { "Fumufumu", "Houhou", "Naninai" };

            var idxH = 0;
            var idxF = 0;

            SectionCommand.Subscribe(p => {
                if (p == "Header")
                {
                    HeaderText.Value = headers[idxH++];
                    if (idxH >= 3)
                    {
                        idxH = 0;
                    }
                }
                else
                {
                    FooterText.Value = footers[idxF++];
                    if (idxF >= 3)
                    {
                        idxF = 0;
                    }
                }
            });

            CellIconSize.Subscribe(x => {
                Debug.WriteLine($"CellIconSizeChange {x.Width} {x.Height}");
            });
        }