列出以间隔返回特定字段的值 [英] List to return values in intervals for a specific field

问题描述

我正在用大量数据实现Telerik Chart.图表的x轴上的标签重叠.我已经解决了这个问题，但长期来看并不可靠.

I am implementing Telerik Chart with a huge data. The labels on x-axis of the chart are overlapping. I have overcome this problem but it is not reliable for long run.

这些是列表具有的字段:

These are the fields List have:

FieldName                DataType
Date                     DATETIME
DateString               STRING
Unit                     DOUBLE
Price                    DOUBLE

X轴标签值来自DateString字段

我实施的解决方案

1. 最小和最大日期DateString"字段将始终返回.
2. 对于其余部分，返回工作日为星期一"的那些值

1. The MIN and MAX Date DateString field will always return.
2. For the rest, return those values where weekday is 'Monday'

这是代码-

// Get min and max Date
DateTime minDate = DateTime.Now;
DateTime maxDate = DateTime.Now;
if (dtGas.Rows.Count > 0)
{
    minDate = Convert.ToDateTime(dtGas.Compute("MIN([Date])", ""));
    maxDate = Convert.ToDateTime(dtGas.Compute("MAX([Date])", ""));
}
// Group by 'Date' and 'DateString' | 'SUM' of Unit and 'Price'
var qGas = from x in dtGas.AsEnumerable()
            group x by new
            {
                Date  = x.Field<DateTime>("Date"),
                DateString = x.Field<string>("DateString")
            } into egroup
            let isOne = egroup.Key.Date.DayOfWeek.ToString() == "Monday"
            select new
            {
                Date = egroup.Key.Date,
                DateString = minDate == egroup.Key.Date ?
                                            (
                                                egroup.Key.DateString
                                            ) :
                                            (
                                                maxDate == egroup.Key.Date ?
                                                (
                                                    egroup.Key.DateString
                                                ) :
                                                ( 
                                                    (isOne) ?
                                                    (
                                                        egroup.Key.DateString
                                                    ) :
                                                    (" ")
                                                )                                            
                                            ),
                Unit = egroup.Sum(r => r.Field<double>("Unit")),
                Price = egroup.Sum(r => r.Field<double>("Price")),
            };

此解决方案有助于返回的不是全部值，而是其中一些值.因此避免重叠.但是将来随着数据的增长，即使这种解决方案也会失败.

This solution helps to return not all values but some of them. Hence avoiding overlapping. But in future as data grows, even this solution will fail.

我需要实施的解决方案

我正在思考但不知道如何实现的想法是-

An idea that I was thinking but don't know how to implement is-

1. 最小和最大日期DateString"字段将始终返回. [与我现在正在做的事情相同]
2. 从MIN和MAX日期开始，以间隔为间隔返回8个值，而不管列表项的总数如何.
   2.a.但是，如果列表计数小于或等于8，则返回所有值.

1. The MIN and MAX Date DateString field will always return. [Same as what I am doing right now]
2. Return 8 values in intervals from MIN and MAX date regardless of total count of List Item.
   2.a. But if List count is less than or equals to 8 then return all values.

例如，如果在列表中，我有32个值.它应该在DateString字段中返回总计10个值，其余的将为空字符串.

So, for example, if in List I have 32 values. It should return me total 10 values in DateString field and rest will be empty string.

推荐答案

我建议这样:

    public static IList<Stock> GetSome(this IList<Stock> input)
    {
        var result = new List<Stock>();
        if (input.Count < 8)
        {
            return input;
        }
        else
        {
            var i = 0;
            for (; i < input.Count; ++i)
            {
                if (i % 8 == 0)
                {
                    result.Add(input[i]);
                }
            }
            if (i % 8 != 0)
            {
                result.Add(input.Last());
            }
        }
        return result;
    }

如果股票不是按时间顺序排列的，我会按日期按日期排序.Sort().

If the Stocks are not in chronological order, I'd call .Sort() by date on them.

您可能希望在代码中添加null和empty集合检查.

You'll probably like to add null and empty collection checking in your code.

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