结合和/或predicateBuilder？ [英] Combine And/Or with PredicateBuilder?

问题描述

我有 IDS 的名单，我只想做一个和放在了第一位，并与或在随后的。在过去，我已经养了柜台变量，当柜台是1，我做的和，但在那之后我做了一个或，但我很好奇，如果有一个更简单的方法：

 的foreach（IDS中的字符串ID）
{
   predicate.And（X =＆GT; id.Contains（x.id））; //我只想在第一个ID做一个和。
}
 

这是我在过去所做的那样，但有一个更简洁的方式：

  INT计数器= 1;
的foreach（在IDS变种标识）
{
     字符串我= ID;
     如果（计数器== 1）
     {
         predicate = predicate.And（X =＆GT; i.Contains（x.id））;
         反++;
      }
      其他
      {
           predicate = predicate.Or（X =＆GT; i.Contains（x.id））;
          反++;
      }
   }
 

解决方案

该作品的predicateBuilder（没有的EntityFramework或LinkToSql可在工作）的本地副本：

  VAR firstID = ids.First（）;
predicate.And（X =＆GT; firstID.Contains（x.id））;

的foreach（在ids.Skip串号（1））
{
    VAR LOCALID = ID; //获得的改性闭合否则
    predicate.Or（X =＆GT; localID.Contains（x.id））;
}
 

I have a list of Ids and I only want to do an AND on the first one and and OR on the subsequent ones. In the past, I have kept a counter variable and when the counter is 1, I do the And, but after that I do an OR, but I was curious if there was an easier way:

foreach(string id in Ids)
{
   predicate.And(x=> id.Contains(x.id)); //I want to do an And only on the first id.
}

This is what I have done in the past, but is there a more concise way:

int counter = 1;
foreach (var Id in Ids)
{
     string i = Id;
     if (counter == 1)
     {
         predicate = predicate.And(x => i.Contains(x.id));
         counter++;
      }
      else
      {
           predicate = predicate.Or(x=>i.Contains(x.id));
          counter++;
      }
   }

解决方案

This works with a local copy of PredicateBuilder (no entityFramework or LinkToSql available at work):

var firstID = ids.First();
predicate.And(x => firstID.Contains(x.id));

foreach (string id in ids.Skip(1))
{
    var localID = id;   //access to a modified closure otherwise
    predicate.Or(x => localID.Contains(x.id)); 
}

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