c# - 具有 lambda 表达式的对象列表中的累积和 C#

Question

我需要使用 lambda 表达式在列表中显示累计和。你知道我该怎么做吗？ 我有这个返回:

[
{
    "dt_created": "2018-02-25",
    "qtNewItens": 1
},
{
    "dt_created": "2018-02-26",
    "qtNewItens": 1
},
{
    "dt_created": "2018-02-27",
    "qtNewItens": 2
}

]

但我必须显示这个:

[
{
    "dt_created": "2018-02-25",
    "qtNewItens": 1
},
{
    "dt_created": "2018-02-26",
    "qtNewItens": 2
},
{
    "dt_created": "2018-02-27",
    "qtNewItens": 4
}

]

我不知道是否可以使用 GroupBy 或聚合

我尝试过这样的事情，但它是错误的:

var newItensByDay = ctx.Itens
                    .GroupBy(x => new { Data = x.dt_created, x.Id })
                    .Select(g => new {
                        Qt = g.Select(x => x.Id).Count(),
                        Dt_created = g.Select(x => x.dt_created).FirstOrDefault()
                    })
                    .GroupBy(x => new { x.Qt, x.Dt_created })
                    .Select(grp => new {
                        dt_created = grp.Key.Dt_created,
                        qtNewItens = grp.Sum(x => x.Qt)
                    });

Answer 1

考虑以下分组后的累积选择

var itemsByDay = ctx.Itens
                    .GroupBy(x => x.dt_created)
                    .Select(g => new {
                        Qt = g.Count(),
                        Dt_created = g.Key
                    });

var count = 0;
var cumulativeByDay = itemsByDay.Select(x => {
    count += x.Qt;
    var result = new {
        dt_created = x.Dt_created,
        qtNewItens = count
    };
    return result;
});