问如何从一年内的月份列表中找出缺少的月份

EN

public class MonthData
{
    public int Month { get; set; }
    public int Money { get; set; }
}

var months = new List<MonthData>
{
    new MonthData {Month = 1, Money = 400},
    new MonthData {Month = 2, Money = 500},
    new MonthData {Month = 4, Money = 550},
    new MonthData {Month = 5, Money = 425},
    new MonthData {Month = 6, Money = 770},
    new MonthData {Month = 7, Money = 500},
    new MonthData {Month = 9, Money = 300},
    new MonthData {Month = 10, Money = 900},
    new MonthData {Month = 11, Money = 440},
    new MonthData {Month = 12, Money = 620}
};

# Find missing months
var missingMonths = Enumerable
    .Range(months.Min(m => m.Month), months.Max(m => m.Month))
    .Except(months.Select(m => m.Month))

# Insert missing months back into months list
foreach (var month in missingMonths)
{
    months.Insert(month - 1, new MonthData { Month = month, Money = 0 });
}

var months = new Dictionary<int, int>
{
    {1, 400},
    {2,500},
    {4, 550},
    {5, 425},
    {6, 770},
    {7, 500},
    {9, 300},
    {10, 900},
    {11, 440},
    {12, 620}
};

var missingMonths = Enumerable
    .Range(months.Keys.Min(), months.Keys.Max())
    .Except(months.Keys);

foreach (var month in missingMonths)
{
    months[month] = 0;
}

var monthList = months
    .Select(pair => new MonthData { 
        Month = pair.Key, 
        Money = pair.Value 
    })
    .OrderBy(m => m.Month)
    .ToList();

// Example
var yearSales = new Dictionary<int, decimal>
{
    {  1, 100 },
    {  3, 300 },
    {  6, 600 },
};

// Actual logic
var fullMonths = Enumerable.Range(1, 12)
    .ToDictionary(
        month => month,
        month => yearSales.TryGetValue(month, out decimal d) ? d : default
    );