Question

我不是linq的最佳人选，但却是首选语言。我正在尝试使用sql编写查询。标准场景我有发票，发票上有发票详细信息。当将表格连接在一起时，具有多个细节的发票将重复进行。在标准的SQL中我可以使用distinct或group by。我试图用linq来关注它，但是得到了错误，或者只是没有过滤掉它们。

这是我的查询

var result = (from invoice in invoices
      join invoiceItem in invItems on invoice.Id equals invoiceItem.InvoiceId
      orderby invoice.InvoiceNo
      select new InvoiceReceiveShipmentVM
      {
          dtInvoiced = invoice.dtInvoiced,
          InvoiceNumber = invoice.InvoiceNo,
          InvoiceType = invoice.InvoiceType,
          InvoiceStatus = invoice.InvoiceStatus,
          Lines = invoiceItem.Line,
          Total = invoice.Total,
          Carrier = invoice.Carrier,
      });
return result.Distinct();

我也试过了：

         var myList = result.GroupBy(x => x.InvoiceNumber)
                            .Select(g => g.First()).ToList();
        return myList.Skip(fetch.Skip).Take(fetch.Take).AsQueryable();

Answer 1

使用distinct，请覆盖InvoiceReceiveShipmentVM中的Equals和GetHashCode

public class InvoiceReceiveShipmentVM
{
    public override bool Equals(object obj)
    {
        if (obj is InvoiceReceiveShipmentVM == false) return false;

        var invoice = (InvoiceReceiveShipmentVM)obj;
        return invoice.InvoiceNumber == InvoiceNumber
            && invoice.InvoiceType == InvoiceType
            && invoice.InvoiceStatus == InvoiceStatus
            && invoice.Lines == Lines
            && invoice.Total == Total
            && invoice.Carrier == Carrier;
    }
    public override int GetHashCode()
    {
        return InvoiceNumber.GetHashCode()
            ^ InvoiceType.GetHashCode()
            ^ InvoiceStatus.GetHashCode()
            ^ Lines.GetHashCode()
            ^ Total.GetHashCode()
            ^ Carrier.GetHashCode();
    }
}

使用linq查询删除重复的行

1 个答案: