LINQ中的LIKE运算子

本文介绍了LINQ中的LIKE运算子的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

与SQL的LIKE运算符类似，有什么方法可以比较C#LINQ表达式中的字符串吗?

Is there any way to compare strings in a C# LINQ expression similar to SQL's LIKE operator?

假设我有一个字符串列表.在此列表中，我想搜索一个字符串.在SQL中，我可以这样写:

Suppose I have a string list. On this list I want to search a string. In SQL, I could write:

SELECT * FROM DischargePort WHERE PortName LIKE '%BALTIMORE%'

查询要使用linq语法，而不是上面的

Instead of the above, query want a linq syntax.

using System.Text.RegularExpressions; … var regex = new Regex(sDischargePort, RegexOptions.IgnoreCase); var sPortCode = Database.DischargePorts .Where(p => regex.IsMatch(p.PortName)) .Single().PortCode;

我上面的LINQ语法不起作用.我怎么了?

My above LINQ syntax does not work. What have I got wrong?

推荐答案

通常使用String.StartsWith/EndsWith/Contains.例如:

var portCode = Database.DischargePorts .Where(p => p.PortName.Contains("BALTIMORE")) .Single() .PortCode;

我不知道是否有一种方法可以通过LINQ to SQL执行正确的正则表达式. (请注意，它确实取决于您使用的提供程序-在LINQ to Objects中会很好；这取决于提供程序是否可以将调用转换为其本机查询格式，例如SQL.)

I don't know if there's a way of doing proper regular expressions via LINQ to SQL though. (Note that it really does depend on which provider you're using - it would be fine in LINQ to Objects; it's a matter of whether the provider can convert the call into its native query format, e.g. SQL.)

正如BitKFu所说的，当您期望一个精确的结果时应使用Single-如果不是这样的话是错误的.应根据期望的确切使用SingleOrDefault，FirstOrDefault或First的选项.

As BitKFu says, Single should be used when you expect exactly one result - when it's an error for that not to be the case. Options of SingleOrDefault, FirstOrDefault or First should be used depending on exactly what's expected.