Question

我有很多笔和很多历史，都有一列a，b，c。
我希望能够使用LINQ进行合并，并具有where条件（日期）。

public async Task<int> CountInPenLot(DateTimeOffset date)
{
    var lotPens = await _context.LotPens.ToListAsync();
    var lotHistory = await _context.LotHistories.ToListAsync();
    // union lotpens and lot history on columns a,b,c where condition date
    //continue my logic

}

Answer 1

由于您只想对c列中的值求和，所以最简单的方法是只运行两个查询并将它们加在一起。

public async Task<int> CountInPenLot(DateTimeOffset date)
{
    var lotPensSum = await _context.LotPens
        .Where(x => x.DateColumn == date) //Filter on the date
        .SumAsync(x => x.c); //Sum up column c

    var lotHistorySum = await _context.LotHistories
        .Where(x => x.DateColumn == date)
        .SumAsync(x => x.c);

    return lotPensSum + lotHistorySum;    
}

Answer 2

我不确定C列的数据类型。如果它不是数字，那么您需要修改代码以检查空值并强制转换类型，然后对其求和。

  public async Task<int> CountInPenLot(DateTimeOffset date)
    {
        int total = 0;
        var lotPensSum = await _context.LotPens
            .Where(x => x.DateColumn == date).toList(); //Filter on the date


        var lotHistorySum = await _context.LotHistories
            .Where(x => x.DateColumn == date).toList();

        foreach (var lotPens in lotPensSum)
        {
            if (lotPens.c != null)
            {
                int intC = 0;
                int.TryParse(lotPens.c, out intC);
                total += intC;
            }
        }

        foreach (var lotHistor in lotHistorySum )
        {
            if (lotHistor.c != null)
            {
                int intC = 0;
                int.TryParse(lotHistor.c, out intC);
                total += intC;
            }
        }

    return total;
    }

如何通过公用列合并两个不同类型的列表？

2 个答案: