Linq2Entity中如何实现Linq2SQL中的SQLMethods.Like查询？

Question

public class Edb : DbContext{
    public Edb() : base("Name=ConnectionString"){}
    public DbSet<Product> Products{get;set;}
}

比如数据库中有以下数据：

1. 东风145加油车(XXX立方)
2. 东风153运油车(XXX立方)
3. .....

我想用LIKE查询“%东风%油车%"，使用SQLMethods.Like和Contains("东风%油车")都不行，有什么方法可以办到！

Answer 1

楼主您好：

我建议您使用where带条件查询：

using(DataEntity entity = new DataEntity())
{
    var result = from item in entity.XXX
                        where item.XXX.Contains("东风") && item.XXX.Contains("油车")
                       select item;
}

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Answer 2

你好 楼主,

你的东方两个字是确保会在最前面的吗？

如果是的话，建议你可以用

where item.XXX.StartWith("东风") && item.XXX.Contains("油车")

如果不是的就参照ThankfulHeart的就可以了。

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Answer 3

楼主，要不你还可以用正则表达式判断，比如：

using (DataEntity entity = new DataEntity())
{
     Regex reg = new Regex("东方.+?车");
     var result = from item in entity.XXX.AsEnumerable()
                         where reg.Match(item.XXX.ToString()).Successful
                         select item;
}

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Answer 4

如果是AsEnumerable()就是在内存中判断了。不是在数据库了。数据量大的话效率极低的

Answer 5

关键字是不确定的，有时甚至是更复杂的。所以我一开始就说不使用StartWith,EndWith,Contains

有没有有办法扩展entityframework，让它支持like语句，如 like 'a%b%c%d%e'

Answer 6

我使用的是EF6,好像不能用  db.table.Where("....")这种方式查询。好像where后面只能是lambada表达式

Answer 7

尝试我的方法了吗？

如果你用Lambda，完全可以：

entity.XXX.AsEnumerable().Where(item=>reg.Match(item.XXX).Success);

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Answer 8

使用AsEnumerable就是把数据全部读到内存中判断的，这样当然是可以！但是这样效率太低。几十万条数据，每条几十个字段

尝试我的方法了吗？

如果你用Lambda，完全可以：

entity.XXX.AsEnumerable().Where(item=>reg.Match(item.XXX).Success);

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Answer 9

您好，

我知道那效率肯定很低，不过考虑到它不怎么支持DB，所以无奈用这个方法……

要不你尝试是否写一个存储过程啥的，在里边调用？

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Answer 10

您好，

我知道那效率肯定很低，不过考虑到它不怎么支持DB，所以无奈用这个方法……

要不你尝试是否写一个存储过程啥的，在里边调用？

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Answer 11

已找到方法：

var items=from a in db.products
  where System.Data.Entity.SqlServer.SqlFunctions.PatIndex("%东风%油车%")>0
select a;

Answer 12

好的，谢谢分享你的答案，我的答案不是最好，请取消标记，谢谢！

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