如何使用LINQ和Entity Framework根據條件設置參數

Question

這是我的代碼：

await ctx.Education.AsNoTracking()
        .Where(e => e.EmployeeNumber == employeeNumber)
        .Select(e => new EducationDTO {
                Id = e.EducationID,
                StartDate =  DbFunctions.CreateDateTime(e.EducationEntryYear , 1, 1, 0, 0, 0) ?? DateTime.Now,
                EndDate = DbFunctions.CreateDateTime(e.EducationGraduationYear, 1, 1, 0, 0, 0),
        })
        .ToListAsync().ConfigureAwait(false);

在某些情況下，“ e.EducationEntryYear”為0，結果返回此異常Conversion failed when converting date and/or time from character string.

如果e.EducationEntryYear為0，將第一個參數作為當前年份的最簡單方法是什么

Answer 1

使用條件（ ? ）運算符。

await ctx.Education.AsNoTracking()
        .Where(e => e.EmployeeNumber == employeeNumber)
        .Select(e => new EducationDTO {
                Id = e.EducationID,
                StartDate =  DbFunctions.CreateDateTime(e.EducationEntryYear == 0 ? DateTime.Now.Year : e.EducationEntryYear, 1, 1, 0, 0, 0) ?? DateTime.Now,
                EndDate = DbFunctions.CreateDateTime(e.EducationGraduationYear, 1, 1, 0, 0, 0),
        })
        .ToListAsync().ConfigureAwait(false);

Answer 2

您目前在哪里

e.EducationEntryYear

替換為

e.EducationEntryYear == 0 ? System.DateTime.Now.Year : e.EducationEntryYear