使用 C# Mongodb 驱动程序在嵌套列表中查找项目

Question

I have a model like this:

Class1 
{
    public List<Class2> Class2List { get; set; }
}

Class2 
{
    public List<Class3> Class3List { get; set; }
}

Class3 
{
    public List<Class4> Class4List { get; set; }
}

Class4 
{
    public int Value { get; set; }
    public DateTime CreateDate{ get; set; }
}

I need to find a list of items of Class4 which are between two dates. I try to use below code but I need to return list of type Class4:

public async Task<IList<Class1>> GetClass4BetweenDates(string Id, DateTime fromDate, DateTime toDate)
{
    var builder = Builders<Class1>.Filter;
    var filter = builder.Eq("Id", Id) & builder.Gte("Class2.Class3.Class4.CreateDate", fromDate) & builder.Lte("Class2.Class3.Class4.CreateDate", toDate);
    return await _context.GetCollection<Class1>().Find(filter).ToListAsync();            
}

I know this is wrong. I need to know the correct way

Answer 1

I think you should try this:

The only problem is in your example that you only give a create date witch elements should be bigger then and smaller then the CreateDate. This is kind off imposible.

public async Task<IList<Class1>> GetClass4BetweenDates(string id, DateTime fromDate, DateTime toDate)
{
    var filterDefinition = Builders<Class1>.Filter.Where(x => x.Id == id &&
                                                              x.Class2List.Any(a => a.Class3List.Any(b => b.Class4List.Any(c => c.CreateDate >= fromDate && 
                                                                                                                                c.CreateDate <= toDate))));
    return await _context.GetCollection<Class1>().Find(filterDefinition).ToListAsync();            
}

Answer 2

To the follow up question to only return the class4 types you can do the following:

public async Task<IList<Class4>> GetClass4BetweenDates(string id, DateTime fromDate, DateTime toDate)
{
    var filterDefinition = Builders<Class1>.Filter.Where(x => x.Id == id &&
                                                              x.Class2List.Any(a => a.Class3List.Any(b => b.Class4List.Any(c => c.CreateDate >= fromDate && 
                                                                                                                                c.CreateDate <= toDate))));
    var class1 = await _context.GetCollection<Class1>().Find(filterDefinition).ToListAsync();  

    var class4List = new List<Class4>();

    if (class1 == null)
        return class4List; 

    foreach (var class2 in class1.Class2List)
    {
        foreach (var class3 in class2.Class3List)
        {
            if (class3.Class4List.Any())
                class4List.AddRange(class3.Class4List);
        }
    }

    return class4List;       
}