chartname.DataSource = EventcategoryopenCount;
chartname.Series["OPEN"].XValueMember = "Key";
chartname.Series["OPEN"].YValueMembers = "Value";
chartname.DataSource = EventcategoryreductCount;
chartname.Series["Close"].XValueMember = "Key";
chartname.Series["Close"].YValueMembers = "Value";
chartname.DataBind();

chartname.Series["OPEN"].Points.DataBind(EventcategoryopenCount, "Key", "Value", "");
chartname.Series["Close"].Points.DataBind(EventcategoryreductCount, "Key", "Value", "");

chartname.DataSource = EventcategoryreductCount;

Series s = new Series("OPEN");
s.XValueMember = "Key";
s.YValueMembers = "Value";
s.ChartType = SeriesChartType.Line;

Series s2 = new Series("Close");
s2.XValueMember = "Key";
s2.YValueMembers = "Value";
s2.ChartType = SeriesChartType.Line;

chartname.Series.Add(s);
chartname.Series.Add(s2);