LINQ to Entities无法识别方法'Char get_Chars(Int32)'，并且该方法无法转换为商店表达式 [英] LINQ to Entities does not recognize the method 'Char get_Chars(Int32)' method, and this method cannot be translated into a store expression

问题描述

我只想从字符串eventTriggers中选择字段为"1"的记录(看起来像这样:"00100010")

I would like to select only the records that have the field "1" from the string eventTriggers (that looks something like this : "00100010" )

我已经尝试并成功地进行了1次以上的呼叫..但我怀疑它的效率.基本上，我会想要这样的东西...但是LINQ显然不支持此功能.
(LINQ to Entities does not recognize the method 'Char get_Chars(Int32)' method, and this method cannot be translated into a store expression.)

I've tried and succesfully done so with more than 1 calls .. but i doubt its efficient. Basically I would want something like this ... but apprently LINQ does not support this.
(LINQ to Entities does not recognize the method 'Char get_Chars(Int32)' method, and this method cannot be translated into a store expression.)

     using (var service = new dB.Business.Service.BaseBusinessService<memo>())
   {
      List<memo> result = service.Repository.GetQuery().Where(p => p.ID == ID && p.eventTriggers[index] == '1').ToList();
   }

是否有正确解决方案的提示?谢谢 ！

Any hints towards the correct solution ? Thank you !

推荐答案

EF无法将char数组操作转换为有效查询.怎么样

EF can't convert the char array operation into a valid query. How about

IEnumerable<Memo> memos
using (var service = new dB.Business.Service.BaseBusinessService<Memo>())
{
    memos = service.Repository.GetQuery()
                    .Where(p => p.ID == ID).AsEnumerable();
}

var result = memos.Where(m => m.eventTriggers[index] == '1').ToList();

这会在本地获取所有具有匹配ID的备忘录，然后在eventTriggers数组上进行过滤.

This gets all the memos with a matching ID locally then filters on the eventTriggers array.

或者，您可以将eventTriggers转换为数值并使用位掩码，这可能是一个更快的查询.

Alternatively you could convert eventTriggers into a numeric value and use a bit mask, this would probably be a much faster query.

Linq看起来像这样

Linq looking like this,

using (var service = new dB.Business.Service.BaseBusinessService<Memo>())
{
    result = service.Repository.GetQuery()
                 .Where(p => 
                         p.ID == ID
                     &&
                         m.eventTriggers & mask != 0).ToList();
}

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