C# LINQ 多行条件

Question

public List<VehicleOnTaskDetailDto> GetVehicleOnTaskDetailFinished(VotFilterRequest filterRequest)
    {
        using VehicleDeliveryContext context = new VehicleDeliveryContext();
            var result = (from v in context.VehiclesOnTask
                join d in context.Departments on v.DepartmentId equals d.Id 
                join dr in context.Drivers on v.DriverId equals dr.Id
                join vehicle in context.Vehicles on v.VehicleId equals vehicle.Id 
                where v.IsDeleted != true
                where v.IsFinished == true
                orderby v.GivenDate descending 
                select new VehicleOnTaskDetailDto{
                    VehicleOnTaskId = v.Id,
                    VehiclePlate = vehicle.Plate,
                    VehicleId = v.VehicleId,
                    DriverName = $"{dr.Name} {dr.Surname} - {dr.Mission}",
                    DepartmentName = d.Name,
                    TaskDefinition = v.TaskDefinition,
                    AuthorizedPerson = v.AuthorizedPerson,
                    Address = v.Address,
                    GivenDate = v.GivenDate,
                    ReturnDate = v.ReturnDate
                }).ToList();
            return result;
    }

我想根据VotFilterRequest自带的DateType过滤器添加2行代码，类似如下所示：

     if (filterRequest.DateType == "GivenDate")
     {
         where filterRequest.FirstDate <= v.GivenDate
         where filterRequest.LastDate >= v.GivenDate
     }
     else
     {
         where filterRequest.FirstDate <= v.ReturnDate
         where filterRequest.LastDate >= v.ReturnDate
     }

我知道你不能这样做，但我也不想重复我的代码。有什么办法可以很快做到这一点吗？谢谢您的问候。

Answer 1

您可以通过使用 LINQ 扩展方法并在构建查询期间使用

IQueryable

轻松实现它：

var query = context.VehiclesOnTask
    // You'd need to define those navigation properties.
    .Include(x => x.Department)
    .Include(x => x.Driver)
    .Include(x => x.Vehicle)
    .Where(x => x.IsDeleted == false)
    .Where(x => x.IsFinished == true);
    
query = filterRequest.DateType == "GivenDate"
    ? query.Where(v => filterRequest.FirstDate <= v.GivenDate && filterRequest.LastDate >= v.GivenDate)
    : query.Where(v => filterRequest.FirstDate <= v.ReturnDate && filterRequest.LastDate >= v.ReturnDate);
    
return query
    .OrderByDescending(x => x.GivenDate)
    .Select(v => new VehicleOnTaskDetailDto
    {
        VehicleOnTaskId = v.Id,
        VehiclePlate = vehicle.Plate,
        VehicleId = v.VehicleId,
        DriverName = $"{dr.Name} {dr.Surname} - {dr.Mission}",
        DepartmentName = d.Name,
        TaskDefinition = v.TaskDefinition,
        AuthorizedPerson = v.AuthorizedPerson,
        Address = v.Address,
        GivenDate = v.GivenDate,
        ReturnDate = v.ReturnDate,
    })
    .ToList();