C＃LINQ當條件如果

我有我試圖重構，因爲它不太好一些LINQ代碼：C＃LINQ當條件如果

基本上，我想知道是否有執行以下一個更好的辦法：

if (!string.IsNullOrWhiteSpace(_filter.AssignedTo) 
{ 
var query = from ticket in dataClassesDataContext.TicketsIssues 
      where ticket.ClosedDate == null 
      && cUser.GetUserNameUsingGUID(ticket.AssignTicketToUser) == _filter.AssignedTo             
      select new 
      { 
       Priority = ticket.TicketPriority.TicketPriorityName, 
       Description = ticket.Description.Replace("\n", ", "), 
      }; 
} 
else 
{ 
var query = from ticket in dataClassesDataContext.TicketsIssues 
      where ticket.ClosedDate == null 
      select new 
      { 
       Priority = ticket.TicketPriority.TicketPriorityName, 
       Description = ticket.Description.Replace("\n", ", "), 
      }; 
}

它們都是相同遠離where子句是用於AssignTicketToUser檢查。

我希望有更好的方法來避免使用if else語句嗎？我有一些這樣的代碼塊，不想重複代碼！

來源

2012-12-14 Belliez

var query = from ticket in dataClassesDataContext.TicketsIssues 
      where ticket.ClosedDate == null 
      && (string.IsNullOrWhiteSpace(_filter.AssignedTo) ? true : cUser.GetUserNameUsingGUID(ticket.AssignTicketToUser) == _filter.AssignedTo)             
      select new 
      { 
       Priority = ticket.TicketPriority.TicketPriorityName, 
       Description = ticket.Description.Replace("\n", ", "), 
      };

你可以擺脫if-else語句的乾脆。將if條件轉移到2nd where子句，並刪除！那第二個條款成爲三元運算符。

如果條件爲真，即如果_filter.AssignedTo爲null，則不要通過返回true來測試_filter.AssignedTo。如果它不爲空或空，則繼續處理原始else塊中的子句。

來源

2012-12-14 02:02:19

而不是'condition1？ true：condition2'你可以寫'（condition1 || condition2）'。 –

謝謝，這正是我正在尋找....並感到尷尬，我沒有想到這個自己（一個新的嬰兒和深夜工作的組合！）。謝謝 – Belliez

一種方式可以是：

var query = from ticket in dataClassesDataContext.TicketsIssues 
      where ticket.ClosedDate == null 
      select new 
      { 
       Priority = ticket.TicketPriority.TicketPriorityName, 
       Description = ticket.Description.Replace("\n", ", "), 
      }; 

if (!string.IsNullOrWhiteSpace(_filter.AssignedTo) 
    query = query.Where(w => cUser.GetUserNameUsingGUID(w.AssignTicketToUser) == _filter.AssignedTo));

來源

2012-12-14 02:02:01 jzm

看看PredicateBuilderimplementation from C# In a Nutshell，And方法應該以更通用的方式解決您的問題，並幫助理解LINQ和表達式樹。你會最終得到類似的東西：

var query = from ticket in dataClassesDataContext.TicketsIssues 
      where ticket.ClosedDate == null 
      select new 
      { 
       Priority = ticket.TicketPriority.TicketPriorityName, 
       Description = ticket.Description.Replace("\n", ", "), 
      }; 

if (!string.IsNullOrWhiteSpace(_filter.AssignedTo)) 
{ 
    query = query.And(ticket => cUser.GetUserNameUsingGUID(ticket.AssignTicketToUser) == _filter.AssignedTo); 
}

來源

2012-12-14 02:42:06

C＃LINQ當條件如果

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