Winform 图表控件未创建正确的折线图

我在使用 Winform 图表控件创建折线图时遇到错误。 （我用的是VS2013）

I'm plotting a line chart and it produces the strange visual effect of a single solid line connecting the first and last points in addition to the correct points.

I don't want the straight line. When I plot this in Excel, I get the correct graph so I know the data series is good.

我已经修改了许多系列设置，但无法让直线消失。这可以解决吗？

我生成该系列的代码如下。感谢您的帮助。

private void numericUpDown1_ValueChanged(object sender, EventArgs e)
    {
        foreach (var series in chart1.Series)
        {
            series.Points.Clear();
        }

        string chartValues = "SELECT statDay, itemCount, [60DayMAVG] FROM tbl_MAVG_dev WHERE streamID = " + numericUpDown1.Value;
        SqlConnection getStreamData = new SqlConnection("Data Source=SQLSERVER;Initial Catalog=MyOwnSQLBox;Integrated Security=True");
        SqlCommand getValuesCMD = new SqlCommand(chartValues, getStreamData);

        try
        {
            getStreamData.Open();
            SqlDataReader getValuesReader = getValuesCMD.ExecuteReader();
            while (getValuesReader.Read())
            {
                //chart1.Series["itemCount"].Points.AddXY(Convert.ToDateTime(getValuesReader.GetDateTime(0)), Convert.ToInt32(getValuesReader.GetInt64(1)));
                chart1.Series["mavg"].Points.AddXY(Convert.ToDateTime(getValuesReader.GetDateTime(0)), Convert.ToInt32(getValuesReader.GetDouble(2)));
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

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