Reportviewer shows blank page after adding a for loop

I have a report that renders perfectly fine when I am populating it with data. I have complex charts, tables and a lot of data (around 20,000 memory objects). My report rendered perfectly fine untill I added a for loop for some data calculation. The for loop is as follows:

         public void InsertLineBreaks(List<LineChart> inputList, int sampleInterval)
        {
            List<LineChart> breaklinesList = new List<LineChart> { };
            for (int i = 1; i <= inputList.Count; i++)
            {
                if ((inputList[i].X - inputList[i - 1].X).TotalMinutes > sampleInterval)
                {
                    LineChart breakline = inputList[i];
                    breakline.BreakLine = 1;
                    breaklinesList.Add(breakline);
                }
                inputList.AddRange(breaklinesList);

            }

This code basically checks if  every data has same interval otherwise adds a breakline. When I add this code, my reportviewer directly shows a blank page without any errors or report controls (next, print, export, etc. buttons). However, if I comment this code out, the report generates just fine without any issues.

I tried debugging the code and put a breakpoint on the data sources. I was surprised to see that the reportviewer still runs and shows a blank page despite the breakpoint. So obviously, the data is not binded and that is why the report viewer is blank.

I suspect reportviewer exceeds the memory allotted to it hence skips my code and data binding and prints blank page. Can anyone help?