System.ArgumentOutOfRangeException when trying to change the color of a cell in a dataGridView

Question

I am trying to build an event management app. I have a window with a month calendar. This is how the DataGridView looks like:

Each cell represents a day month and if one ore more events are scheduled for that day, the cell has to be colored green. I use the following setter:

public IList<Event> _EventsByMonth
{//this setter populates and colors the table
    set
    {
        eventsByMonth = value;


        dgvEventsByMonth.Rows.Add("", "", "", "", "", "", "");
        dgvEventsByMonth.Rows.Add("", "", "", "", "", "", "");
        dgvEventsByMonth.Rows.Add("", "", "", "", "", "", "");
        dgvEventsByMonth.Rows.Add("", "", "", "", "", "", "");
        dgvEventsByMonth.Rows.Add("", "", "", "", "", "", "");
        //dgvEventsByMonth.Rows.Add("", "", "", "", "", "", "");


        foreach (DataGridViewRow row in dgvEventsByMonth.Rows)
        {
            row.Height = (dgvEventsByMonth.ClientRectangle.Height - dgvEventsByMonth.ColumnHeadersHeight) / dgvEventsByMonth.Rows.Count;
        }


        if (eventsByMonth.Count != 0)
        {
            DateTime aux = new DateTime();


            mapMonthDaysToEvents();

            {
                //in case the first event in the list is recurrent, the following method is necessary
                aux = getNextOccurrenceDateOrStartDate(eventsByMonth[0]);
                //I need to know which is the first weekday of the month 
                aux = aux.AddDays(1 - eventsByMonth[0].startDatetime.Day);
            }

            int firstWeekDayOfTheMonth = (int)aux.DayOfWeek;
            int numberOfDays = DateTime.DaysInMonth(aux.Year, aux.Month);

            for (int i = 0, DaysIterator = 1; DaysIterator <= numberOfDays; i++)
            {
                for (int j = 0; j < 7; j++)
                {
                    //go over the uncovered days at the beginning of the calendar
                    while (i == 0 && j + 1 < firstWeekDayOfTheMonth)
                    {
                        j += 1;
                    }

                    dgvEventsByMonth.Rows[i].Cells[j].Value = DaysIterator;

                    //TODO check for events in that day. if any, color the cell
                    /*if (mappingOfMonthDaysToEventsByMonth[DaysIterator] != null)
                    {
                        dgvEventsByDay.Rows[i].Cells[j].Style.BackColor = Color.Green;
                    }*/

                    DaysIterator++;
                }
            } 
        }
        dgvEventsByMonth.Refresh();
    }
}

Besides setting a private field eventsByMonth, this one should also populate and color the datagridview. The above calendar window image resulted when the following code snippet was commented:

                    //TODO check for events in that day. if any, color the cell
                    /*if (mappingOfMonthDaysToEventsByMonth[DaysIterator] != null)
                    {
                        dgvEventsByDay.Rows[i].Cells[j].Style.BackColor = Color.Green;
                    }*/

The following exception was thrown when the same code was uncommented:

Exception thrown: 'System.ArgumentOutOfRangeException' in mscorlib.dll
System.Transactions Critical: 0 : <TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Critical"><TraceIdentifier>http://msdn.microsoft.com/TraceCodes/System/ActivityTracing/2004/07/Reliability/Exception/Unhandled</TraceIdentifier><Description>Unhandled exception</Description><AppDomain>EventManagementApplication.vshost.exe</AppDomain><Exception><ExceptionType>System.ArgumentOutOfRangeException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType><Message>Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index</Message><StackTrace>   at System.Collections.ArrayList.get_Item(Int32 index)
   at System.Windows.Forms.DataGridViewCellCollection.get_Item(Int32 index)
   at EventManagementApplication.CalendarView.set__EventsByMonth(IList`1 value) in D:\probleme in C C++ Java PHP Python\probleme in C C++ Java PHP Python\C#\EventManagementApplication\EventManagementApplication\View\CalendarView.cs:line 225

What is the problem, given the fact that the statement dgvEventsByMonth.Rows[i].Cells[j].Value = DaysIterator; above the problematic snippet never throws an exception ?

When the exception is thrown i==3, j==5, DaysIterator==23.

Should I try other method to color a cell? I do not want to get stuck on this one. For me it is more important to make things work than solving this kind of problem.

Answer 1

You iterate over dgvEventsByMonth, but set style for cell in dgvEventsByDay. As far as I understand, you need to replace it