[英]How to use Linq to check if a list of strings contains any string in a list
[英]How do you check if a string contains any strings from a list in Entity Framework?
我正在嘗試搜索數據庫以查看字符串是否包含搜索詞列表的元素。
var searchTerms = new List<string> { "car", "232" };
var result = context.Data.Where(data => data.Name.Contains(searchTerms) ||
data.Code.Contains(searchTerms));
如果 searchTerms 是一個字符串,這將起作用,但我一直試圖讓它與字符串列表一起使用。
本質上我需要 SQL 會說
SELECT * FROM Data
WHERE Name LIKE '%car%'
OR Name LIKE '%232%'
OR Code LIKE '%car%'
OR Code LIKE '%232%'
linq list contains any in list似乎是我能找到的最接近這種情況的東西。
Where(data => searchTerms.Contains(data.Name) || searchTerms.Contains(data.Code)
僅將完全匹配項帶回搜索詞列表。
我也嘗試在實體框架中搜索多個關鍵字搜索,並且已經用盡了努力。 有什么方法可以實現我的目標嗎?
您可以嘗試使用Any
方法,我不確定它是否受支持,但值得嘗試:
var result = context.Data.Where(data => searchTerms.Any(x => data.Name.Contains(x)) ||
searchTerms.Any(x => data.Code.Contains(x));
如果這給您NotSupportedException
您可以在Where
之前添加AsEnumerable
以獲取所有記錄並在內存而不是數據庫中執行查詢。
我遲到了,但是使用SearchExtensions nuget 包,您可以執行以下操作
var result = context.Data.Search(x => x.Name, x => x.Code).Containing(searchTerms);
這將構建一個表達式樹,因此仍將在服務器上(而不是在內存中)執行查詢,並且本質上將運行您想要的上述 SQL
以下是一個功能齊全的示例,說明如何使用多個關鍵字實現不同類型的搜索。
這個例子特別針對@Hamza Khanzada 關於Pomelo.EntityFrameworkCore.MySql
的類似問題。
它執行類似於名為@NinjaNye 的庫的功能。
EqualsQuery()
使用了最簡單的方法,它只是根據關鍵字的精確匹配來測試數據庫字段(盡管大小寫無關緊要)。 這是@Mohsen Esmailpour 的建議。
它生成類似於以下的 SQL:
SELECT `i`.`IceCreamId`, `i`.`Name`
FROM `IceCreams` AS `i`
WHERE LOWER(`i`.`Name`) IN ('cookie', 'berry')
ORDER BY `i`.`IceCreamId`
但是,對於您的情況,這可能還不夠,因為您不是在尋找完全匹配的內容,而是希望返回包含僅包含關鍵字(以及可能還有其他詞)的字段的行。
AndContainsQuery()
使用了第二種方法,它仍然非常簡單,但做了一些稍微不同的事情。 它只返回包含所有關鍵字(可能還有其他詞)的結果。
它生成類似於以下的 SQL:
set @__keyword_0 = 'Cookie';
set @__keyword_1 = 'choco';
SELECT `i`.`IceCreamId`, `i`.`Name`
FROM `IceCreams` AS `i`
WHERE
(LOCATE(LCASE(@__keyword_0), LCASE(`i`.`Name`)) > 0) AND
(LOCATE(LCASE(@__keyword_1), LCASE(`i`.`Name`)) > 0)
ORDER BY `i`.`IceCreamId`;
這不是您想要的,但我認為展示也很好,因為它非常簡單,無需手動構建表達式樹即可完成。
最后,第三種方法由orContainsQuery()
,並手動構建部分表達式樹。 它構造多個嵌套OR
表達式的WHERE
表達式的主體。 這就是你想要的。
它生成類似於以下的 SQL:
set @__keyword_0 = 'berry';
set @__keyword_1 = 'Cookie';
SELECT `i`.`IceCreamId`, `i`.`Name`
FROM `IceCreams` AS `i`
WHERE
(LOCATE(LCASE(@__keyword_0), LCASE(`i`.`Name`)) > 0) OR
(LOCATE(LCASE(@__keyword_1), LCASE(`i`.`Name`)) > 0)
ORDER BY `i`.`IceCreamId`;
這是功能齊全的控制台項目:
using System;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Pomelo.EntityFrameworkCore.MySql.Storage;
namespace IssueConsoleTemplate
{
public class IceCream
{
public int IceCreamId { get; set; }
public string Name { get; set; }
}
public class Context : DbContext
{
public DbSet<IceCream> IceCreams { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder
.UseMySql(
"server=127.0.0.1;port=3306;user=root;password=;database=so60914868",
b => b.ServerVersion(new ServerVersion("8.0.20-mysql")))
.UseLoggerFactory(
LoggerFactory.Create(
b => b
.AddConsole()
.AddFilter(level => level >= LogLevel.Information)))
.EnableSensitiveDataLogging()
.EnableDetailedErrors();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<IceCream>(
entity =>
{
entity.HasData(
new IceCream {IceCreamId = 1, Name = "Vanilla"},
new IceCream {IceCreamId = 2, Name = "Berry"},
new IceCream {IceCreamId = 3, Name = "Strawberry"},
new IceCream {IceCreamId = 4, Name = "Berry & Fruit"},
new IceCream {IceCreamId = 5, Name = "cookie"},
new IceCream {IceCreamId = 6, Name = "Chocolate chip cookie"},
new IceCream {IceCreamId = 7, Name = "Choco-Cookie & Dough"});
});
}
}
internal class Program
{
private static void Main()
{
using (var context = new Context())
{
context.Database.EnsureDeleted();
context.Database.EnsureCreated();
}
EqualsQuery();
AndContainsQuery();
OrContainsQuery();
}
private static void EqualsQuery()
{
//
// This will find only matches that match the word exactly (though case-insensitive):
//
using var context = new Context();
var keywords = new[] {"Cookie", "berry"}
.Select(s => s.ToLower())
.ToArray();
var equalsResult = context.IceCreams
.Where(i => keywords.Contains(i.Name.ToLower()))
.OrderBy(i => i.IceCreamId)
.ToList();
Debug.Assert(equalsResult.Count == 2);
Debug.Assert(
equalsResult[0]
.Name == "Berry");
Debug.Assert(
equalsResult[1]
.Name == "cookie");
}
private static void AndContainsQuery()
{
//
// This will find matches, that contain ALL keywords (and other words, case-insensitive):
//
using var context = new Context();
var keywords = new[] {"Cookie", "choco"};
var andContainsQuery = context.IceCreams.AsQueryable();
foreach (var keyword in keywords)
{
andContainsQuery = andContainsQuery.Where(i => i.Name.Contains(keyword, StringComparison.CurrentCultureIgnoreCase));
}
var andContainsResult = andContainsQuery
.OrderBy(i => i.IceCreamId)
.ToList();
Debug.Assert(andContainsResult.Count == 2);
Debug.Assert(
andContainsResult[0]
.Name == "Chocolate chip cookie");
Debug.Assert(
andContainsResult[1]
.Name == "Choco-Cookie & Dough");
}
private static void OrContainsQuery()
{
//
// This will find matches, that contains at least one keyword (and other words, case-insensitive):
//
using var context = new Context();
var keywords = new[] {"Cookie", "berry"};
// The lambda parameter.
var iceCreamParameter = Expression.Parameter(typeof(IceCream), "i");
// Build the individual conditions to check against.
var orConditions = keywords
.Select(keyword => (Expression<Func<IceCream, bool>>) (i => i.Name.Contains(keyword, StringComparison.OrdinalIgnoreCase)))
.Select(lambda => (Expression) Expression.Invoke(lambda, iceCreamParameter))
.ToList();
// Combine the individual conditions to an expression tree of nested ORs.
var orExpressionTree = orConditions
.Skip(1)
.Aggregate(
orConditions.First(),
(current, expression) => Expression.OrElse(expression, current));
// Build the final predicate (a lambda expression), so we can use it inside of `.Where()`.
var predicateExpression = (Expression<Func<IceCream, bool>>)Expression.Lambda(
orExpressionTree,
iceCreamParameter);
// Compose and execute the query.
var orContainsResult = context.IceCreams
.Where(predicateExpression)
.OrderBy(i => i.IceCreamId)
.ToList();
Debug.Assert(orContainsResult.Count == 6);
Debug.Assert(orContainsResult[0].Name == "Berry");
Debug.Assert(orContainsResult[1].Name == "Strawberry");
Debug.Assert(orContainsResult[2].Name == "Berry & Fruit");
Debug.Assert(orContainsResult[3].Name == "cookie");
Debug.Assert(orContainsResult[4].Name == "Chocolate chip cookie");
Debug.Assert(orContainsResult[5].Name == "Choco-Cookie & Dough");
}
}
}
您可以使用Linq中的Any函數來查看數據中是否包含任何術語。
var result = context.Data.Where(data => searchTerms.Any(term => data.Name.Contains(term) ||
searchTerms.Any(term => data.Code.Contains(term));
該請求將在數據庫端執行
var searchTerms = new List<string> { "car", "232" };
Expressions<Func<Data, bool>> expression = it => false;
foreach(var searchTerm in searchTerms)
{
expression = expression.Or(it => it.Name.Contains(searchTerm));
//you can implement your own 'Or' extensions method,
//or use third-party libraries, i.e. LinqKit
}
var result = context.Data.Where(expression);
您還可以使用規范模式,以實現代碼純度
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.