7

我有一个<string变量计数的列表>,我想查询(通过 LINQ)一个表来查找包含文本列中任何这些字符串的任何项目。

试过这个(不起作用):

items = from dbt in database.Items
         where (stringList.FindAll(s => dbt.Text.Contains(s)).Count > 0)
         select dbt;

查询将类似于:

select * from items where text like '%string1%' or text like '%string2%'

这可能吗?

4

4 回答 4

11

看看这篇文章做你想做的事:
http

://www.albahari.com/nutshell/predicatebuilder.aspx 这就像一个梦。我基本上剪切并粘贴了他们的代码并将其取回(当然使用我自己的数据方案):

SELECT [t0].[Id], [t0].[DateCreated], [t0].[Name] ...
FROM [dbo].[Companies] AS [t0]
WHERE ([t0].[Name] LIKE @p0) OR ([t0].[Name] LIKE @p1)

这是我为概念验证运行的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;

namespace PredicateTest
{
class Program
{
    static void Main(string[] args)
    {
        DataClasses1DataContext dataContext = new DataClasses1DataContext();

        Program p = new Program();
        Program.SearchCompanies("test", "test2");
        var pr = from pi in  dataContext.Companies.Where(Program.SearchCompanies("test", "test2")) select pi;
    }

    DataClasses1DataContext dataContext = new DataClasses1DataContext();

    public static Expression<Func<Company, bool>> SearchCompanies(
                                                  params string[] keywords)
    {
        var predicate = PredicateBuilder.False<Company>();
        foreach (string keyword in keywords)
        {
            string temp = keyword;
            predicate = predicate.Or(p => p.Name.Contains(temp));
        }
        return predicate;
    }

}

public static class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T>() { return f => true; }
    public static Expression<Func<T, bool>> False<T>() { return f => false; }

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
                                                        Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>
              (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
                                                         Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>
              (Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
    }
}
}

我建议去该网站获取代码和解释。

(我将留下第一个答案,因为如果您需要 IN 语句,它会很好地工作)

于 2009-02-06T15:49:18.053 回答
6

对整个 LINQ to SQL 游戏来说是一种新事物,但是这种语法有帮助吗?

string[] items = new string[] { "a", "b", "c", "d" };

var items = from i in db.Items
             where items.Contains(p.text)
            select i;

得到它:

http://blog.wekeroad.com/2008/02/27/creating-in-queries-with-linq-to-sql/

于 2009-02-04T17:15:29.287 回答
1

阅读这篇文章后,寻找与您相同的解决方案,我发现使用 Linq 的.Anyand.All方法的解决方案是一种简单而优雅的方式来获取数组的匹配结果。

在本例中,我使用搜索输入,以逗号分隔作为示例。我不在乎比赛是否在同一情况下。

var qry = Query.Split(',').Select(c => c.Trim().ToLower());

首先获取一些要查询的数据,从 Linq 到 SQL 或任何地方

var search = db.tablename;

使用 lambda 语法编写紧凑的代码,并导致.Any查询中的字符串与表中的名称或描述匹配。

search = search.Where(
    record => 
    qry.Any(q => record.Name.ToLower().Contains(q)) || 
    qry.Any(q => record.Description.ToLower().Contains(q)));

如果您只想要在任何字段中匹配所有字符串的结果,您可以替换.Any.All

search = search.Where(
    record => 
    qry.All(q => record.Name.ToLower().Contains(q)) || 
    qry.All(q => record.Description.ToLower().Contains(q)));
于 2011-06-30T14:25:53.537 回答
0

使用:

string searh = "test1 test2,test3";    
data.Persons.Search(p => p.Name, search);

搜索功能是:

public static IQueryable<T> Search<T>(this IQueryable<T> source, Expression<Func<T, string>> selector, string s)
{
    if (string.IsNullOrEmpty(s))
        return source;

    string[] str = s.Split(new char[] { ' ', ',' }, StringSplitOptions.RemoveEmptyEntries);

    MethodInfo methodContains = typeof(string).GetMethod("Contains", new[] { typeof(string) });

    Expression strExpression;
    Expression expressionContains;
    Expression resultExpression = Expression.Empty();

    for (int i = 0; i < str.Length; i++)
    {
        strExpression = Expression.Constant(str[i].Trim(), typeof(string));
        expressionContains = Expression.Call(selector.Body, methodContains, strExpression);

        if (i == 0)
            resultExpression = expressionContains;
        else
            resultExpression = Expression.OrElse(resultExpression, expressionContains);
    }

    Expression<Func<T, bool>> lambdaExpr = Expression.Lambda<Func<T, bool>>(resultExpression, new ParameterExpression[] { selector.Parameters[0] });

    return source.Where(lambdaExpr);
}
于 2014-02-08T14:57:54.437 回答