LINQ To SQL 异常:本地序列不能用于查询运算符的 LINQ to SQL 实现，但包含运算符除外 [英] LINQ To SQL exception: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains operator

问题描述

考虑这个 LINQ To SQL 查询.其目的是获取一个字符串[] 搜索词并将这些词应用于 SQL 表上的一堆不同字段:

Consider this LINQ To SQL query. It's intention is to take a string[] of search terms and apply the terms to a bunch of different fields on the SQL table:

string[] searchTerms = new string[] {"hello","world","foo"};
List<Cust> = db.Custs.Where(c => 
   searchTerms.Any(st => st.Equals(c.Email))
|| searchTerms.Any(st => st.Equals(c.FirstName))
|| searchTerms.Any(st => st.Equals(c.LastName))
|| searchTerms.Any(st => st.Equals(c.City))
|| searchTerms.Any(st => st.Equals(c.Postal))
|| searchTerms.Any(st => st.Equals(c.Phone))
|| searchTerms.Any(st => c.AddressLine1.Contains(st))
)
.ToList();

引发异常:

本地序列不能在 LINQ to SQL 的查询运算符实现中使用，除了 Contains() 运算符

Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator

问题:为什么会引发这个异常，如何重写查询来避免这个异常?

Question: Why is this exception raised, and how can the query be rewritten to avoid this exception?

推荐答案

在您的查询中将 Any 的用法替换为 Contains.例如:

Replace the usages of Any with Contains in your query. eg:

searchTerms.Contains(c.Email)

这应该会得到您正在寻找的结果.它向后看，但它是正确的——它会为包含 searchTerms 中的所有元素的每个字段生成一个 IN 运算符.

This should get the result you're looking for. It looks backwards, but it's correct- it'll generate an IN operator for each field inside a Contains with all the elements in searchTerms.

AddressLine1 部分​​不会以这种方式工作 - 您必须自己使用

The AddressLine1 part won't work this way- you'll have to loop-generate the comparisons yourself with

c.addressLine1.Contains(...)

PredicateBuilder 之类的东西对此会有帮助.

Something like PredicateBuilder can be helpful for this.

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