x轴值在.net图表中不正确

Question

for (int i = 0; i < 2; i++)
{
    chart.Series.Add("SS" + i);
}

for (int i = 0; i < dtRpt.Rows.Count; i++)
{
    chart.Series[0].Points.AddXY(dtRpt.Rows[i].ItemArray[0], dtRpt.Rows[i].ItemArray[4]);
    chart.Series[1].Points.AddXY(dtRpt.Rows[i].ItemArray[0], dtRpt.Rows[i].ItemArray[5]);
    System.Drawing.Color col = System.Drawing.ColorTranslator.FromHtml("#3F66B1");
    System.Drawing.Color col1 = System.Drawing.ColorTranslator.FromHtml("#DD3B26");
    chart.Series[0].Color = col;
    chart.Series[1].Color = col1;
}

图表的图像某些图表x轴不可见;任何人都可以帮我解决。