HasValue使EF查詢無效-有解無憂

當前查詢（下一個）的問題是 if request.DepartmentId.HasValueis false。我想要做的基本上就是在“From”到“To”期間找到屬于 DepartmentId 和 RoomType 匹配的可用房間。

public async Task<Response> Handle(GetAvailableRoomsQuery request, CancellationToken cancellationToken)
{
    // We are getting all class activities between From and To
    var classActivities = await _sender.Send(
        new GetClassActivitiesQuery
        {
            From = request.From,
            To = request.To
        }, cancellationToken);

    // finding all unavailable rooms between From and To
    var unavailableRoomIds = new HashSet<int>(classActivities.Select(e => e.RoomId));

    return await _context.Rooms
        .Where(room => !unavailableRoomIds.Contains(room.Id) &&
                        request.DepartmentId.HasValue && request.DepartmentId.Value == room.DepartmentId &&
                        request.RoomType.HasValue && request.RoomType.Value == room.Type)
        .ProjectTo<RoomDto>(_mapper.ConfigurationProvider)
        .ToListAsync(cancellationToken);
}

這是以前可以作業的查詢，但有 3 個 Where 陳述句。

public async Task<Response> Handle(GetAvailableRoomsQuery request, CancellationToken cancellationToken)
{
    var classActivities = await _sender.Send(
        new GetClassActivitiesQuery
        {
            From = request.From,
            To = request.To
        }, cancellationToken);

    var unavailableRoomIds = new HashSet<int>(classActivities.Select(e => e.RoomId));

    return await _context.Rooms
        .Where(room => !unavailableRoomIds.Contains(room.Id))
        .Where(room => !request.DepartmentId.HasValue || request.DepartmentId.Value == room.DepartmentId)
        .Where(room => !request.RoomType.HasValue || request.RoomType.Value == room.Type)
        .ProjectTo<RoomDto>(_mapper.ConfigurationProvider)
        .ToListAsync(cancellationToken);
}

uj5u.com熱心網友回復：

正如@juharr 所提到的：

return await _context.Rooms
    .Where(room => !unavailableRoomIds.Contains(room.Id))
    .Where(room => !request.DepartmentId.HasValue || request.DepartmentId.Value == room.DepartmentId)
    .Where(room => !request.RoomType.HasValue || request.RoomType.Value == room.Type)

應該相當于：

return await _context.Rooms
    .Where(room => !unavailableRoomIds.Contains(room.Id)) &&
                  (!request.DepartmentId.HasValue || request.DepartmentId.Value == room.DepartmentId) &&
                  (!request.RoomType.HasValue || request.RoomType.Value == room.Type))

真的不明白為什么您將||s 更改為&&s 并洗掉了!s

轉載請註明出處，本文鏈接：https://www.uj5u.com/shujuku/494613.html

標籤：C＃。网数据库实体框架 qrs

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