How to customize ASP.Net chart - asp.net

Question

Am creating ASP.NET Report for my Application.
i want the X-AXIS of my graph to display Timeperiod in this format:eg
1990-2000,2000-2010,2010-2020 etc.
protected void Page_Load(object sender, EventArgs e)
{
SqlConnection DBconnection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString2"].ToString());
SqlCommand sqlCmd = new SqlCommand("select YEAR(ValidityFrom) as SpecYear,COUNT(DocumentTypeID) as Total From Document WHERE ValidityFrom is not null AND DocumentTypeID = 1 Group by YEAR(ValidityFrom)", DBconnection);
SqlDataReader reader;
try
{
DBconnection.Open();
reader = sqlCmd.ExecuteReader();
while (reader.Read())
{
SumID.Series["summery-id"].Points.AddXY(reader["SpecYear"], reader["Total"]);
}
reader.Close();
}
catch (SqlException err)
{
for (int i = 0; i < err.Errors.Count; i++)
{
lblErrorMessage.Text = ("Message: " + err.Errors[i].Message + "\n" +
"LineNumber: " + err.Errors[i].LineNumber + "\n" +
"Error-Code: " + err.ErrorCode.ToString() + "\n" +
"Or Connection To server Fail");
}
}
catch (NullReferenceException err)
{
lblErrorMessage.Text = ("Error:" + err.Message + "\n" +
"Source :" + err.Source +
"Method:" + err.TargetSite);
}
catch (Exception err)
{
lblErrorMessage.Text = "Error Reading Data " + err.Message;
}
finally
{
DBconnection.Close();
}