将 SQL 语句转换为 Linq 表达式

Question

我对 linq 和 .net 内核很陌生。 作为我最后一年项目的一部分，我正在尝试计算公司的下一个纳税申报日期。

1. 如果有一个新成立的公司还没有纳税（意味着税表中没有条目），则在公司成立日期上增加18个月。
2. 如果公司已经缴纳了税款，则从税表中选择最晚的日期 TaxReturnDate 并添加 9 个月以获得下一个 TaxReturnDate。

这就是我在 SQL 中尝试过的，现在我正在尝试将此 sql 转换为 Linq 查询，我需要一些帮助才能获得所需的结果。

 WITH cte_company (CompanyID, CompanyName, CompanyNumber, IncorporatedDate, TOTAL_YEARS) AS (SELECT CompanyID, CompanyName, CompanyNumber, IncorporatedDate, DATEDIFF(YEAR, IncorporatedDate, CURRENT_TIMESTAMP) AS TOTAL_YEARS FROM tbl_Company) SELECT cte_company.CompanyID, CompanyName, CompanyNumber, IncorporatedDate, TOTAL_YEARS, CASE WHEN TOTAL_YEARS > 1 THEN (SELECT DATEADD(MONTH, 9, MAX(TaxReturnDate)) FROM tbl_Tax WHERE cte_company.CompanyID = tbl_Tax.CompanyID) ELSE DATEADD(MONTH, 18, IncorporatedDate) END AS TaxDate FROM cte_company

Linq查询

IEnumerable<CompanyTaxInfo> result = from c in this.AcmeDB.tbl_Company let TotalYears = (DateTime.Now - c.IncorporatedDate).Value.Days / 365 let taxReturnDate = this.AcmeDB.tbl_Tax.Max(tx => tx.TaxReturnDate).Value.AddMonths(9) select new CompanyTaxInfo { CompanyID = c.CompanyID, CompanyName= c.CompanyName, CompanyNumber= c.CompanyNumber, IncorporatedDate= c.IncorporatedDate, TotalYears = TotalYears, TaxDate = TotalYears > 1? taxReturnDate: c.IncorporatedDate.Value.AddMonths(21) }; return result;

代码抛出 DbArithmeticExpression arguments must have a numeric common type。 例外。

请帮忙

Answer 1

尝试以下查询：

 var query = from c in this.AcmeDB.tbl_Company let TotalYears = EF.Functions.DateDiffYear(c.IncorporatedDate, DateTime.Now) select new CompanyTaxInfo { CompanyID = c.CompanyID, CompanyName = c.CompanyName, CompanyNumber = c.CompanyNumber, IncorporatedDate = c.IncorporatedDate, TotalYears = TotalYears, TaxDate = TotalYears > 1? this.AcmeDB.tbl_Tax.Where(tax => c.CompanyId == tax.CompanyId).Max(tx => tx.TaxReturnDate).Value.AddMonths(9): c.IncorporatedDate.Value.AddMonths(18) }; return query.ToList();