Hide zero level on Y-Axis in chart

Hi
I am creating a line chart on a win form where y axis does not show zero level. I have tried setting diagram.AxisY.WholeRange.AlwaysShowZeroLevel = false and setting min max range, nothing seems to work so far. Could you please help.
I have attached a sample project that has  this issue. Please take a look. I am working on version 14.1

C#
private void Form1_Load(object sender, EventArgs e) {  

            // Create a chart control.  
            //ChartControl chartControl1 = new ChartControl();  

            // Add the chart to the form.  
            //chartControl1.Dock = DockStyle.Fill;  
            //this.Controls.Add(chartControl1);  
            chartControl1.Series.Clear();  
            // Create a bar series and add points to it.  
            Series series1 = new Series("Series 1", ViewType.Line);  
            series1.ArgumentScaleType = ScaleType.DateTime;  
            DateTime d1 = DateTime.Now;  
            d1.AddDays(-1);  
            series1.Points.Add(new SeriesPoint(d1, new double[] { 26.25 }));  
            series1.Points.Add(new SeriesPoint(d1.AddDays(2), new double[] { 1.52 }));  
            series1.Points.Add(new SeriesPoint(d1.AddDays(3), new double[] { 22.21 }));  
            series1.Points.Add(new SeriesPoint(d1.AddDays(4), new double[] { 15.35 }));  
            series1.Points.Add(new SeriesPoint(d1.AddDays(5), new double[] { 4.15 }));  

            // Add the series to the chart.  
            chartControl1.Series.Add(series1);  

            // Cast the chart's diagram to the XYDiagram type, to access its axes.  
            XYDiagram diagram = (XYDiagram)chartControl1.Diagram;  

            // Enable the diagram's scrolling.  
            diagram.EnableAxisXScrolling = true;  
            diagram.EnableAxisYScrolling = true;  

            // Define the whole range for the X-axis.  
            diagram.AxisX.WholeRange.Auto = true;  
            //diagram.AxisX.WholeRange.SetMinMaxValues("A", "D");  

            // Disable the side margins  
            // (this has an effect only for certain view types).  
            diagram.AxisX.VisualRange.AutoSideMargins = false;  

            // Limit the visible range for the X-axis.  
            diagram.AxisX.VisualRange.Auto = true;  
            //diagram.AxisX.VisualRange.SetMinMaxValues("B", "C");  

            // Define the whole range for the Y-axis.  
            diagram.AxisY.WholeRange.Auto = false;  
            diagram.AxisY.WholeRange.AlwaysShowZeroLevel = true;  
            diagram.AxisY.WholeRange.SetMinMaxValues(1,  26.25 );  
        }  

Edit 1:  

Series series1 = new Series("Series 1", ViewType.Line);  
            series1.ArgumentScaleType = ScaleType.DateTime;  
             series1.ValueScaleType = ScaleType.Numerical;  

            series1.Points.Add(new SeriesPoint(new DateTime(2015,9,15),15 ));  
            series1.Points.Add(new SeriesPoint(new DateTime(2016, 9, 15), 10));  
            series1.Points.Add(new SeriesPoint(new DateTime(2017, 7, 15), 21));  
            series1.Points.Add(new SeriesPoint(new DateTime(2018, 9, 15), 16));  
            series1.Points.Add(new SeriesPoint(new DateTime(2020, 5, 15), 600));  

            // Add the series to the chart.  
            chartControl1.Series.Add(series1);  

            // Cast the chart's diagram to the XYDiagram type, to access its axes.  
            XYDiagram diagram = (XYDiagram)chartControl1.Diagram;  

            // Enable the diagram's scrolling.  
            diagram.EnableAxisXScrolling = false;  
            diagram.EnableAxisYScrolling = false;  

            // Define the whole range for the X-axis.  
            diagram.AxisX.WholeRange.Auto = false;  
            diagram.AxisX.Label.TextPattern = "{A:d}";  
            diagram.AxisX.WholeRange.SetMinMaxValues(new DateTime(2015,5,15), new DateTime(2021, 5, 15));  

            // Disable the side margins  
            // (this has an effect only for certain view types).  
            diagram.AxisX.VisualRange.AutoSideMargins = false;  

            // Limit the visible range for the X-axis.  
            diagram.AxisX.VisualRange.Auto = false;  
            //diagram.AxisX.VisualRange.SetMinMaxValues("B", "C");  

            // Define the whole range for the Y-axis.  
            //diagram.AxisY.WholeRange.Auto = false;  
            diagram.AxisY.WholeRange.SideMarginsValue = 0;  
            diagram.AxisY.WholeRange.SetMinMaxValues(5, 650);