LINQ – 如果条件

发布时间：2020-12-12 07:47:32 所属栏目：MsSql教程来源：网络整理

导读：在代码中,注释部分是我需要解决的问题…有没有办法在LINQ中编写这样的查询？我需要这个,因为我需要根据状态进行排序. var result = ( from contact in db.Contacts join user in db.Users on contact.CreatedByUserID equals user.UserID join deal in db.Dea

在代码中,注释部分是我需要解决的问题…有没有办法在LINQ中编写这样的查询？我需要这个,因为我需要根据状态进行排序.

var result = (
     from contact in db.Contacts
     join user in db.Users on contact.CreatedByUserID equals user.UserID
     join deal in db.Deals on contact.ContactID equals deal.ContactID into deals
     orderby contact.ContactID descending
     select new ContactListView
     {
         ContactID = contact.ContactID,FirstName = contact.FirstName,LastName = contact.LastName,Email = contact.Email,Deals = deals.Count(),EstValue = deals.Sum(e => e.EstValue),SalesAgent = user.FirstName + " " + user.LastName,Tasks = 7,// This is critical part
         if(Deals == 0) Status = "Prospect";
         else
             Status = "Client";
         // End of critical part...
     })
     .OrderBy(filterQuery.OrderBy + " " + filterQuery.OrderType)
     .Where(filterQuery.Status);

解决方法

Status = (deals.Count() == 0 ? "Prospect" : "Client")

这使用了“Conditional operator”

The conditional operator (?:) returns
one of two values depending on the
value of a Boolean expression.

编辑：你可以像这样组合：

Status = (deals.Count() == 0 ? "Prospect" : (deals.Count() == 1 ? "Client" : "Other"))

在这种情况下,您正在使用deals.Count(),因此您可以使用LINQ let语法将结果存储在临时变量中：

var result = (
   from contact in db.Contacts
   join user in db.Users on contact.CreatedByUserID equals user.UserID
   join deal in db.Deals on contact.ContactID equals deal.ContactID into deals
   let dealCount = deals.Count()
   ... // Continue here
     Status = (dealCount == 0 ? "Prospect" : (dealCount == 1 ? "Client" : "Other"))

（编辑：李大同）

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