First I'm pretty sure that plus signs are Markers and not ChartTypes.
I know for sure that stars and diamonds are.
You could do a List and save in it all the line ChartType (ex Spline, Line, etc) and looping while binding the data
SqlDataAdapter adapter = new SqlDataAdapter(query2, connection);
DataSet ds = new DataSet();
adapter.Fill(ds);
int i = 0;
foreach (DataRow dr in ds.Tables[0].Rows)
{
Series series = new Series();
series.Points.AddXY(dr["Date"], dr["Shipments"]);
series.ChartType = yourChartTypeList[i];
i++;
Chart1.Series.Add(series);
}
(here using a DataSet)
or afterwards
//already bound
int i = 0;
foreach (Series s in Chart1.Series)
{
s.ChartType = yourChartTypeList[i];
i++;
}
that way if you want to add something to the series, like tooltip or whatever you'll have a place to do that.