我如何优化这个lambda表达式,使用实体框架查询包含单词列表的每行
本文关键字:查询 框架 实体 包含单 列表 何优化 优化 表达式 lambda | 更新日期: 2023-09-27 18:15:45
我有一些输入,像这样:"Steve Brian McFistycuffs Johnson"
,我想在我的数据库中查找,并返回所有包含这些单词的记录,以任何顺序。
我要做的是,像
var matches = myContext.MyTable.Where( c => c.Name.Contains("Steve") && c.Name.Contains("Brian") && c.Name.Contains("McFistycuffs") && c.Name.Conains("Johnson"));
但是,我需要动态地执行此操作,并且单词的数量可能会改变。
我还想确保无论我选择什么,它都不会影响实体框架创建SQL语句,例如。我想确保它尽可能地优化它。这意味着在lambda内做某种foreach可能不会工作,因为实体框架不能轻松地将其映射到SQL。
有什么建议吗?
类似于
static void Main()
{
string[] words = {"abc", "def"};
var filter = ContainsAllWords<Person>(x => x.Name, words);
// same as: x => x.Name.Contains("abc") && x.Name.Contains("def")
// then:
var rows = myContext.MyTable.Where(filter);
}
static Expression<Func<T,bool>> ContainsAllWords<T>(
Expression<Func<T, string>> selector, string[] words)
{
if (words == null || words.Length == 0) return x => true;
Expression body = Expression.Call(selector.Body, "Contains", null,
Expression.Constant(words[0], typeof(string)));
for (int i = 1; i < words.Length; i++)
{
body = Expression.AndAlso(body,
Expression.Call(selector.Body, "Contains", null,
Expression.Constant(words[i], typeof(string))));
}
return Expression.Lambda<Func<T, bool>>(body, selector.Parameters);
}
var list = new[] { "Brian", "Steve", "Johnson" };
var x = myContext.MyTable.Where(c => list.All(p => c.Name.Contains(p)))
str = "Steve Brian McFistycuffs Johnson"
string[] strParts = str.Split(' ');
myContext.MyTable.Where(c => strParts.All(part => c.Name.contains(part )))
var arr = new string[] {"Steve","Brian","McFistycuffs","Johnson"};
var matches = myContext.MyTable.Where(c =>arr.All(ar => ar==c.Name));
可能是以下内容?
string inputFull = "Steve Brian McFistycuffs Johnson";
string[] stringSeparators = new string[] {" "};
var matches = myContext.MyTable;
foreach(string input in inputFull.Split(stringSeparators, StringSplitOptions.None))
{
matches = matches.Where(c => c.Name.Contains("input"))
}
编辑:从上面的答案中使用。all()会更好。
胡乱猜测…使用正则表达式怎么样?
(代码未测试)
var input = "Steve Brian McFistycuffs Johnson";
var re = new Regex(input.Replace(" ","|"));
var matches = myContext.MyTable.Where( c => re.IsMatch(c.Name));