c# - Linq中基于过滤器的动态分组

Question

我有两个过滤器。一个是按月、年、日分组，另一个过滤器是选择是否有人想按产品或公司分组。也可以有更多的过滤器。现在一开始我写了 if else 用于特定条件，如下所示。

List<IGrouping<String, TopItemReportData>> GroupedData = new List<IGrouping<String, TopItemReportData>>();

if (filters.DateBy.ToLower().Replace(" ", "") == "yearlyreport")
    GroupedData = topsalesQueryable.GroupBy(x => x.SalesDate.Year.ToString()).OrderByDescending(x => x.Sum(y => y.SellingQuantity)).Skip((filters.CurrentPage - 1) * filters.RecordsPerPage).Take(filters.RecordsPerPage).ToList();
else if (filters.DateBy.ToLower().Replace(" ", "") == "monthlyreport")
    GroupedData = topsalesQueryable.GroupBy(x => x.SalesDate.Month.ToString()).OrderByDescending(x => x.Sum(y => y.SellingQuantity)).Skip((filters.CurrentPage - 1) * filters.RecordsPerPage).Take(filters.RecordsPerPage).ToList();
else
    GroupedData = topsalesQueryable.GroupBy(x => x.SalesDate.Date.ToString()).OrderByDescending(x => x.Sum(y => y.SellingQuantity)).Skip((filters.CurrentPage - 1) * filters.RecordsPerPage).Take(filters.RecordsPerPage).ToList();

if (filters.GroupBy.ToLower().Replace(" ", "") == "variantoption")
    GroupedData = topsalesQueryable.GroupBy(x => (x.VariantId).ToString()).OrderByDescending(x => x.Sum(y => y.SellingQuantity)).Skip((filters.CurrentPage - 1) * filters.RecordsPerPage).Take(filters.RecordsPerPage).ToList();
else if (filters.GroupBy.ToLower() == "product")
    GroupedData = topsalesQueryable.GroupBy(x => (x.ProductId).ToString()).OrderByDescending(x => x.Sum(y => y.SellingQuantity)).Skip((filters.CurrentPage - 1) * filters.RecordsPerPage).Take(filters.RecordsPerPage).ToList();

但这行不通，因为现在我必须根据选定的过滤器值同时按年份和产品分组。所以我不知道用什么来替换字符串，因为当我尝试这样做时编译器会给出错误:

GroupedData = topsalesQueryable.GroupBy(x => new {x.SalesDate.Year.ToString(),x.ProductId.ToString()}).OrderByDescending(x => x.Sum(y => y.SellingQuantity)).Skip((filters.CurrentPage - 1) * filters.RecordsPerPage).Take(filters.RecordsPerPage).ToList();

该匿名类型成员必须使用成员赋值声明。我的问题是如何摆脱 if else 以及如何解决这个错误

Answer 1

您需要的只是一个包含年份和产品 ID 的字符串。

我们有一个非常简单的方法来创建它:

string.Format("{0:0000}|{1:000000}", x.SalesDate.Year, x.ProductId)

冒号后的零表示字段的大小，以防 ProductId 长度不同。

整个事情(清理了一下)将是:

void Main()
{
    var filters = new Filters();
    var topsalesQueryable = new List<TopItemReportData>();
    var TopItemReportData = new List<TopItemReportData>();
    IEnumerable<IGrouping<String, TopItemReportData>> tempGroupedData;

    var dateBy = filters.DateBy.ToLower().Replace(" ", "");
    var groupBy = filters.GroupBy.ToLower().Replace(" ", "");


    if ( dateBy  == "yearlyreport")
    {
        if (groupBy ==  "product")
            tempGroupedData = TopItemReportData
                               .GroupBy(x =>string.Format("{0:0000}|{1:000000}",
                                         x.SalesDate.Year, x.ProductId));
        else
           tempGroupedData = TopItemReportData.GroupBy(x => x.SalesDate.Year.ToString());
    }
    else if (dateBy == "monthlyreport")
        tempGroupedData = topsalesQueryable.GroupBy(x => x.SalesDate.Month.ToString());
    else
        tempGroupedData = topsalesQueryable.GroupBy(x => x.SalesDate.Date.ToString());

    if (groupBy == "variantoption")
        tempGroupedData = topsalesQueryable.GroupBy(x => x.VariantId.ToString());
    else if (groupBy == "product")
        tempGroupedData = topsalesQueryable.GroupBy(x => x.ProductId.ToString());

    var GroupedData = tempGroupedData
                            .OrderByDescending(x => x.Sum(y => y.SellingQuantity))
                            .Skip((filters.CurrentPage - 1) * filters.RecordsPerPage)
                            .Take(filters.RecordsPerPage)
                            .ToList();
}

class Filters
{
    public string DateBy;
    public string GroupBy;
    public int CurrentPage;
    public int RecordsPerPage;

    public Filters()
    {
        DateBy = "Yearly Report";
        GroupBy = "variantoption";
    }

}

class TopItemReportData
{
    public DateTime SalesDate;
    public int SellingQuantity;
    public int VariantId;
    public int ProductId;
}

您仍然需要理顺 if/elses，但我认为最好的方法是消除 DateBy 属性并只使用 GroupBy。