[Chartjs]-How to sort MMMYY on Chart.Js and display the values that match the month?

You could change your linq like below:

public JsonResult OnGetRevenueData()
{
    var year = _context.year.Select(a => a.Month).ToList();
    var Revenue = (from t in _context.Revenue
                    where year.Contains(t.Month)
                    group t by new {  Month = t.Month} into g                              
                    select new 
                    {
                        Amount = g.Sum(a => a.Amount),
                        Month = g.Key.Month
                    }).ToList();
    var countRevenue = Revenue.OrderBy(a => DateTime.ParseExact(a.Month, "MMMyy", CultureInfo.InvariantCulture).Month)
                                .Select(a=>a.Amount)
                                .ToList();
    var countPayroll = (from t in _context.payroll
                        where year.Contains(t.Month)
                        group t by new { Month = t.Month } into g
                        select new {
                            Amount = g.Sum(a => a.Amount),
                            Month = g.Key.Month
                        }).ToList();
    var countPayable = (from t in _context.payable
                        where year.Contains(t.Month)
                        group t by new { Month = t.Month } into g
                        select new
                        {
                            Amount = g.Sum(a => a.Amount),
                            Month = g.Key.Month
                        }).ToList();
      //change here......
    var leftOuterJoin = from a in countPayable
                        join b in countPayroll on a.Month equals b.Month into temp
                        from count in temp.DefaultIfEmpty()
                        select new
                        {
                            Month = a.Month,
                            Amount = a.Amount
                        };
    var rightOuterJoin =
        from b in countPayroll
        join a in countPayable on b.Month equals a.Month into temp
        from count in temp.DefaultIfEmpty()
        select new
        {
            Month = b.Month,
            Amount = b.Amount
        };
    var fullOuterJoin = leftOuterJoin.Union(rightOuterJoin);
    var Expense = (from t in fullOuterJoin
                    group t by new
                    {
                        Month = t.Month
                    } into g
                    select new
                    {
                        Amount = g.Sum(a => a.Amount),
                        Month = g.Key.Month
                    }
                    ).ToList();
    var countExpense = Expense.OrderBy(a => DateTime.ParseExact(a.Month, "MMMyy", CultureInfo.InvariantCulture).Month)
                                .Select(a => a.Amount)
                                .ToList();

    var yearList = ((from y in _context.year
                        select y.Month
                        )
                    .AsEnumerable()
                    .OrderBy(s => DateTime.ParseExact(s, "MMMyy", CultureInfo.InvariantCulture).Month)
                    ).ToArray();
    return new JsonResult(new { revenue = countRevenue, expense = countExpense, month = yearList });
}

Result:

Bar Chart:

payable table:

payroll table:

Revenue table:

year table: