将 SQL 语句转换为 Linq 表达式

Question

I am quite new to linq and .net core. I am trying to calculate the next tax return date of a company as a part of my final year's project.

1. If there is a newly made company with no tax has been made yet (means no entry in the tax table), Then add 18 months in the company's incorporated date.
2. If the company has already paid tax, then pick the latest date TaxReturnDate from tax table and add 9 months into that to get the next TaxReturnDate.

Thats what i have tried in SQL, now i am trying to convert this sql into Linq Query, I need some help to get the desired results.

 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 Query

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;

code is throwing DbArithmeticExpression arguments must have a numeric common type.' exception.

Please help

Answer 1

Try the following query:

 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();