在 Linq 中加入、分組和求和

Question

我想通過employeeId對員工的加班時間進行分組，並獲取employeeNames數據和員工每月加班總時數。 但是這個 Linq 查詢給出了翻譯錯誤。

var results = 
    from overtime in context.Overtimes
    join employeeCredential in context.EmployeeCredentials
        on overtime.EmployeeId equals employeeCredential.id
    join employeeDetail in context.EmployeeDetails
        on employeeCredential.id equals employeeDetail.employeeId
    where overtime.Month == month && overtime.Year == year
    group new { overtime, employeeCredential, employeeDetail } by overtime.EmployeeId into g
    select new MonthlyOvertimeWorkHours
    {
        EmployeeName = g.First().employeeDetail.employeeName,
        TotalWorkHourOfMonth = g.Sum(t => t.overtime.OvertimeWorkHour)
    };

錯誤

{ "error": employeeCredential\r\n IsNullable: True\r\n, \r\n employeeDetail = EntityShaperExpression: \r\n EntityType: EmployeeDetail\r\n ValueBufferExpression: \r\n ProjectionBindingExpression: employeeDetail\r\n IsNullable: True\r\n }\r\n.Select(s => s.employeeDetail.employeeName)\r\n.First()' 無法翻譯。 以可翻譯的形式重寫查詢，或通過插入對“AsEnumerable”、“AsAsyncEnumerable”、“ToList”或“ToListAsync”的調用顯式切換到客戶端評估。 }

Answer 1

在 EF Core 6 之前，您無法在分組后訪問記錄（這通常很糟糕）。 只有聚合和Key可用。

要解決問題，只需將employeeName添加到分組鍵。

var results = 
    from overtime in context.Overtimes
    join employeeCredential in context.EmployeeCredentials
        on overtime.EmployeeId equals employeeCredential.id
    join employeeDetail in context.EmployeeDetails
        on employeeCredential.id equals employeeDetail.employeeId
    where overtime.Month == month && overtime.Year == year
    group new { overtime, employeeCredential, employeeDetail } by new { overtime.EmployeeId, employeeDetail.employeeName } into g
    select new MonthlyOvertimeWorkHours
    {
        EmployeeName = g.Key.employeeName,
        TotalWorkHourOfMonth = g.Sum(t => t.overtime.OvertimeWorkHour)
    };