c# - Invoking a plot method in Point Collection class -

i'm trying plot data using window form, invoking delegate, plotted xy graph using button fire/initiate event (see code below).

i don't understand why code works plotting xy points doesn't work when want plot y points solely.

what mean plotting y solely i.e. x = 0 , 1, ,2, 3, 4, incrementing 1 or in general fixed increment , can 0.1 or 0.01 , or anything. y passed in user.

using system.windows.forms; using system.windows.forms.datavisualization.charting;  namespace plottingsomedata {     public partial class form1 : form     {         public form1()         {             initializecomponent();         }          // delegate         private delegate int plotxydelegate(double x, double y);          // parameter chart, series of chart, x,y values of graph         private void plotxyappend(chart chart, series dataseries, double x, double y)          {             // invoke delegate passing in add points method in point collection object             chart.invoke(new plotxydelegate(dataseries.points.addxy), new object[] { x, y });         }           double[] x = { 1, 2, 3, 4, 5, 6 };         double[] y = { 1, 2, 3, 4, 5, 6 };          private void button2_click(object sender, eventargs e)         {             (int = 0; < x.length || < y.length; i++)             {                 plotxyappend(this.chart2, this.chart2.series[0], x[i], y[i]);             }         }          //up line... code below doesn't work.         private delegate int plotydelegate(double x, double y);          private void plotyappend(chart chart, series dataseries, double y)         {             // same here fails... adding single y value.              // there error invoking line. don't know problem is.             chart.invoke(new plotydelegate(dataseries.points.addy), new object[] { y });         }      } } 

error: no overload 'addy' matches delegate 'plotsomedata.form1.plotydelegate sorry program work, need add button , chart toolbox .