Question

根据linq查询中检索到的其他几个“列”设置状态的最佳做法是什么。

  var result = (from q in query
                select new Item
                         {
                           ApprovedDate = q.ApprovedDate,
                           CreatedDate = q.CreatedDate,
                           DeclinedDate = q.DeclinedDate,
                           Status = 0
                         });

我想将状态设置为0,1,2。

(ApprovedDate == null and DeclinedDate == null) --> 0
(ApprovedDate != null and DeclinedDate == null) --> 1
(DeclinedDate != null) --> 3

或许类似于：

  var result = (from q in query
                select new Item
                         {
                           ApprovedDate = q.ApprovedDate,
                           CreatedDate = q.CreatedDate,
                           DeclinedDate = q.DeclinedDate,
                           Status = (q.CreatedDate == null && q.DeclinedDate == null) ? 0 : (q.ApprovedDate != null && q.DeclinedDate == null) ? 1 : 2
                         });

我可能会添加更多的状态组合，所以我应该尝试在linq select查询中，在我的存储库对象中执行此操作。或者稍后在控制器中我将执行.ToList（）然后预览列表设置正确的状态代码？

如果有超过3个状态代码，则linq查询会“难以”阅读。

Answer 1

如何将状态计算移动到Item级？如果status属性依赖于其他属性值，那么它肯定是计算属性：

var result = from q in query
             select new Item
                         {
                           ApprovedDate = q.ApprovedDate,
                           CreatedDate = q.CreatedDate,
                           DeclinedDate = q.DeclinedDate
                         });

和

public class Item
{
  // other properties

  public int Status
  {
      get
      {
          if (ApprovedDate == null and DeclinedDate == null)
              return 0;
          if (ApprovedDate != null and DeclinedDate == null)
              return 1;
          if (DeclinedDate != null)
              return 3;
          // etc
      }
  }
}

实际上我认为这是最好的选择，因为在这种情况下，状态计算逻辑将接近所需的数据。如果（出于某种原因）您无法使用此方法，请将设置状态移至本地项目集合：

var items = result.ToList().ForEach(i => i.Status = CalculateStatus(i));

Answer 2

也许包裹在一个函数中一个像这样做的linq

var result = (from q in query sele q).AsEnumerable()
                                       .Select( x => new Item()
                                       {
                                           ApprovedDate = x.ApprovedDate,
                                           CreatedDate = x.CreatedDate,
                                           DeclinedDate = x.DeclinedDate,
                                           Status = MyStatusFunction(x.CreatedDate,q.DeclinedDate)
                                       });


public int MyStatusFunction(DateTime ApprovedDate , Datetime DeclinedDate)
{
    if (ApprovedDate == null and DeclinedDate == null) return 0;
    else if(ApprovedDate != null and DeclinedDate == null) return 1;
    else if (DeclinedDate != null) return 3;
}

linq条件查询

2 个答案: